Read The Manual
|Updated January 20, 2007|
Pacemakers are small electrical generators that control your heart beat. They are often just called pacers. You may need a pacemaker if you have a chronic rhythm problem. The pacemaker is one sealed unit, with a battery, some circuitry, and a connector block inside.
The battery supplies the power. The circuitry is like a little computer inside the pacemaker - it changes energy from the battery into tiny electrical pulses that go to your heart through wires called leads. The connector block is plastic, on top of the pacemaker. That's where the leads connect to the generator unit.
One specific kind of pacemaker can help about 1 in 5 heart failure patients feel a lot better. Although many types of heart problems may require a pacer, I am concentrating on one kind - the type specifically for CHFers. This kind of pacemaker therapy is called VRT for "ventricular resynchronization therapy" or CRT for "cardiac resynchronization therapy." The kind of pacemaker used is called a "biventricular pacemaker" because it "paces" both your heart's ventricles (pumping chambers).
CRT is when a pacemaker is used to coordinate your heart's 4 chambers to act together as a team, making them pump blood more efficiently. Many CHFers' hearts don't have all chambers firing at just the right time to beat effectively. Re-timing the beat of some of the chambers can restore that needed teamwork, making your heart function better, which makes you feel better.
Getting the right and left ventricle to beat with proper timing can really improve your heart function, if they aren't already beating properly. Not everyone with heart failure will improve with CRT.
Will CRT help me? - You'll need an EKG read by a cardiologist to see if you fall into the will-benefit or won't-benefit group. VRT was recently FDA-approved so the patient selection process is still an art, not a science. Roughly speaking, there are 3 things that show you will benefit from a VRT pacer:
Patients do not have to strictly meet all 3 of these standards to get a VRT pacer. However, these are the patients most likely to benefit. If your heart's chambers are already beating in proper timing - just beating weakly - there is nothing for a VRT pacer to correct, so you won't benefit. That's why patient selection for CRT is really important.
The EKG (also called ECG or electrocardiogram) monitors the heart's electrical activity. The first wave on an EKG is the P wave. It records the electrical activity of the upper heart chambers. The second and largest wave - the QRS wave - records the electrical activity of the ventricles. The third wave is the T wave. It records the heart's return to a resting state between beats.
How the heart's electrical system works - First, you need to know how it should work. Here are the basics: Heart muscle cells are not like other muscle cells in many ways. It takes a nerve impulse to make a regular muscle cell contract. A heart cell can contract all by itself. The heart muscle cells that do this produce electrical signals that spread throughout the heart. It is these electrical signals that give you a nice steady heart beat.
How does a pacemaker take over your heart beat? - Both parts of the pacing system are inside your body: the generator and the leads. The generator is connected to your heart through the tiny wires called leads. Each lead has an electrode on its tip. That tip actually burrows into your heart wall, either with tines that catch on the inside of your heart wall, or with a screw end that screws into your heart wall. This does no damage and you can't feel it.
The pacer's electrical pulses travel through these leads to your heart. The pulses are timed to flow at regular intervals just like your heart's natural electrical signals would. Your pacer has 2 functions: pacing and sensing. The third part of the system is the programmer. It's like a desktop computer and your doctor uses it in his office to communicate with your pacemaker's software.
Why CRT might - or might not - help you - When some or all of the electrical signals from your SA node don't make it to the ventricles, the team work of the heart's chambers becomes sloppy. The heart is one tough monkey, though. Even if impulses from the upper chambers are blocked, the ventricles will still beat, because fibers in the ventricles can produce their own rhythm. However, this kind of rhythm is pretty slow. If it gets too slow, you don't get enough blood flow. This is called "bundle block."
LBBB, or Left Bundle Branch Block, is when the electrical signal hits the right side properly, then casually wanders over to the left side - late. This causes the right side to contract before the left side does, screwing up the team work. This results in reduced heart output, mitral valve regurgitation, and some funky heart wall motion when the heart beats. None of this is good.
You can also have RBBB or Right Bundle Branch Block, which is the same problem, only with the sides reversed. If you have this kind of heart block, you may be helped by CRT therapy using one of these newly approved pacemakers.
The implant - If you are take a blood thinner like Coumadin, you may be asked to stop taking it several days before the implant procedure. You won't be allowed to eat or drink anything after midnight the day before. You may take your regular meds with a tiny amount of water the morning of the procedure, but ask your doctor about this. You'll need to get to the hospital a couple of hours before implant time.
To get you ready, the nurse will start an IV line, possibly shave part of your chest, give you an antibiotic, and have you sign 6,000 papers. ;-) Then you'll be wheeled to the EP lab, where you get some happy juice through your IV line. Pillows are placed under your legs to help the blood return to your heart. This is for the doctor's benefit, not yours. Your arms will be restrained so you don't raise them up during the implant.
You get to wear a surgical cap like on the show ER, and you get hooked up to monitors to check your heart rhythm, blood pressure, and oxygen level. A nurse will then scrub the skin on your chest with germ killing soap, and place an antibacterial adhesive over the place they are going to cut.
You'll be mostly out of it from the IV juice during the procedure. The doctor numbs the area with a local anesthetic so you don't shout when the cut is made - that would be bad form. <g> He cuts a vein and threads the pacer leads through the vein until the tip of each lead is in the right spot inside your heart. He is using a special kind of x-ray to see where the leads go.
He then surgically creates a small, hollow, "pocket" in the upper chest area, which he cleans with a sterile solution. This leaves a scar about 3 inches long. The pacer generator unit goes in this "pocket" and the leads are attached to the generator. Then the incisions are closed and bandaged.
You'll need to have your arm in a sling for awhile after this so you don't shake everything loose using your arm. You'll probably have to stay in bed until the next day and will be in the hospital a day or two. A chest x-ray may be done to double-check your pacer leads. Your pacemaker will be programmed by the doctor to handle your specific needs.
You will usually be able to go home one to two days after the implant. Your doctor will see you in his office in a couple of weeks to check you out. He can monitor your pacemaker's function through the telephone, but that's standard stuff explained by your doc.
How is CRT pacing different than other pacing? - I am speaking here about Medtronics' InSync pacer system for people with heart failure. One pacer lead goes into into the right atrium, one goes into the right ventricle, and a third lead is needed to pace the left ventricle.
The catch is that leads really shouldn't be put into the left ventricle. Why not? The left ventricle is the heart's main pumping chamber, so it contains high pressures. This means that foreign objects inside it could cause complications such as stroke. InSync gets around this problem. The doctor can see a "road map" of your veins using dye and an x-ray-like camera, so he can plan how to make this work before threading the third lead toward your heart.
The left ventricular lead goes through your coronary sinus, a really big blood vessel which empties into the right atrium. This lead is positioned as far from the right ventricular lead as possible.
The doctor is also taking electrical measurements, looking for a spot behind your left ventricle that has a low "threshold." A "threshold" is the level of power needed to make a pulse do its work in that part of your heart. Less than 2 volts is preferred because that will make your pacer battery last longer. The pacer is set to twice the threshold level to make sure it signal gets where it needs to go.
A current InSync pacer set at 2.5 volts in the atrium and 5 volts in the ventricle will last a little over 6 years. After that, a new pacer is implanted because - like an ICD - the pacer and battery are one sealed unit. Anyway, once the left ventricular lead is set in a spot with a low threshold, the other 2 leads are placed - one in the right atrium and one in the right ventricle.
Then all 3 leads are plugged into the pulse generator and you're good to go.
What happens when the battery dies? - The battery is sealed in the same unit as the generator. A current InSync battery should last about 6 years. The doctor will check it every time he sees you, using the programmer. If the battery gets pretty low, a beeper inside the pacemaker itself starts beeping so you know to get yourself to the doctor right away.
Living with your pacemaker - Before leaving the hospital after your implant, you will be given specific instructions about everything: showering, driving, returning to work, and so on. You will get an ID card to put in your wallet, clearly stating that you have a pacemaker, and giving details.
You can be around (and operate) many appliances such as: microwave ovens, hair dryers, clothes washers and dryers, vacuum cleaners, toasters, blenders and food processors, radios, stereos (don't linger around the speakers though), and televisions. Ask your doctor for a complete list and use the links on this page for more information.
Please note that increasing use of certain magnets can hurt your device and you. See ICDs and pacemakers can be affected by hidden magnets
Some pacemaker history - Since the late 1950s, when pacemakers were first implanted in humans, more than 2 million people have received one. Pacers from the 1950s plugged into an AC power supply - a wall outlet! That meant patients could only travel as far as their extension cord. If a power failure occurred, well, bye-bye. Obviously something better was needed.
In 1957, battery powered pacemakers hit the scene and progress started rolling along. Now you could wear your pacemaker and power failure no longer meant certain death. In 1960, a pacer was implanted completely inside a person for the first time. Look Ma - no wires!
A few years later, leads that went into the heart were developed. This meant no more open-heart surgery to implant a pacer; The whole process got a lot easier for the patient. A few years later still, the "demand" pacer walked onstage. All pacemakers are now demand pacers, meaning they pace your heart only when it needs pacing.
Sometime in the 1970s, lithium batteries made a huge difference in how long you could use a pacer before needing a replacement. Titanium became the metal of choice for the casing and epoxies sealed it all up tight. Now you could use a microwave oven safely even with an implanted pacer. Now, that's progress! <g>
Using radio waves to program the pacer was the next big step. Now you no longer had your chest opened up to get your pacer reprogrammed. Dual chambered pacers soon followed, letting multiple heart chambers be controlled. In the 1980s several developments improved the pacer, including leads that released anti-inflammatory drugs and pacers that adjust to your activity level.
Current pacers are small, light, and streamlined compared to the models shown here, one from 1961 on the right and also the very first Medtronic's implantable pacemaker from the 1950s on the left.
January, 2007 - Can CHFers with a narrow QRS interval (less than 120 ms) benefit from CRT (BiV pacemaker)? Using an echo to measure how well the heart's 4 chambers beat together as a team during systole can show if dysynchrony exists. If it does, a BiV pacemaker will probably help.
Researchers studied 102 class 3 and class 4 CHFers. Fifty-one had wide QRS (greater than 120 ms) and 51 had narrow QRS (less than 120 ms). A form of echo called TDI (Tissue Doppler Imaging) was used to find those CHFers with systolic dysynchrony. Echos were done at study start and 3 months after CRT began.
Systolic LV volume significantly improved in all CRT patients - both narrow-QRS patients and wide-QRS patients.. All CRT patients improved in heart class, ability to exercise (Vo2max), 6-minute walk distance, EF, and mitral valve leakage.
CRT was then turned off (the pacemaker turned off) for 4 weeks. Benefits were then lost but regained when CRT pacing was restarted. Biventricular pacing in CHFers with narrow QRS intervals and dysynchrony as shown on echo do benefit. Their benefit is as great as in CHFers with wide QRS and dysynchrony.
Other researchers also studied CRT use. They studied CHFers with both narrow QRS interval and LV dysynchrony as shown by TDI. Thirty-three consecutive CHFers with narrow QRS intervals and 33 other consecutive CHFers with wide QRS were included. All had LV dysynchrony measured by TDI. All were class 3 or class 4, and had EF less than 36%.
QRS at study start had nothing to do with LV dyssynchrony. Both narrow-QRS and wide-QRS patients had similar improvements in symptoms, LV improvement, and heart class, which improved by a full class in all CRT patients. Average LV end-systolic volume improved 39 ml in narrow-QRS patients and 44 ml in wide-QRS patients.
Researchers have also shown that TDI done by different technicians on different kinds of echo machines all give reliable results in showing dysynchrony. This means it can be spotted at most medical centers and cardiologist offices if doctors and techs are on the ball - very good news for us CHFers. Now using echo (TDI) to spot dysychrony seems much more important then QRS interval to see which CHFers will benefit from BiV pacemakers.
Source: J Am Coll Cardiol. 2006 Dec 5;48(11):2251-7.
Title: Benefits of cardiac resynchronization therapy for heart failure patients with narrow QRS complexes and coexisting systolic asynchrony by echocardiography.
Authors: Yu CM, Chan YS, Zhang Q, Yip GW, Chan CK, Kum LC, Wu L, Lee AP, Lam YY, Fung JW.
Source: Echocardiography. 2007 Jan;24(1):40-6.
Title: Reliability of echocardiographic indices of dyssynchrony.
Authors: Gabriel RS, Bakshi TK, Scott AG, Christiansen JP, Patel H, Wong SP, Armstrong GP.
Source: J Am Coll Cardiol. 2006 Dec 5;48(11):2243-50. Epub 2006 Nov 9.
Title: Cardiac resynchronization therapy in patients with a narrow QRS complex.
Authors: Bleeker GB, Holman ER, Steendijk P, Boersma E, van der Wall EE, Schalij MJ, Bax JJ.
October, 1996 - Angina and poor blood supply to the heart are common in HCM. Dual chamber pacing improves these patients. We studied the effects of permanent dual chamber pacing on heart function in people with HCM.
Six HCM patients with severe had a dual chamber pacer implanted. Heart function and pumping reserve were measured by PET scan after pacemaker implant, and again 3 months later. Results were compared to those from 28 healthy volunteers. Pacing reduced angina pain and also reduced pressure in the ventricles from 65mmHg to 19mmHg. Pacing eased the heart's work load at rest and during a chemical stress test.
Title: Effects of permanent dual chamber pacing on myocardial perfusion in symptomatic hypertrophic cardiomyopathy
Authors: Posma JL, Blanksma PK, Van Der Wall EE, Vaalburg W, Crijns HJ, Lie KI
Source: Heart 1996 Oct;76(4):358-362
PMID: 8983685, UI: 97105577
March 11, 1999 - Studies suggest that 20 to 30% of CHF patients have hearts whose chambers do not beat in a coordinated way. These patients also have a wide QRS on their EKG (ECG) tests. Biventricular pacing forces the ventricles to beat in proper relation to each other. Two trials are studying biventricular pacing in DCM patients.
The VIGOR CHF Trial studies heart function and symptoms in CHFers using biventricular pacing. To test for placebo effects, patients are randomized to get either biventricular pacing or no pacing therapy for the first 6 weeks; then both groups are paced. In other words, they all get pacemakers but they don't know whether theirs is turned on during the first part of the trial or not.
The VENTAK CHF trial uses an ICD to give constant biventricular pacing and treat ventricular tachycardias. All patients use a standard ICD plus heart failure drug therapy throughout the study. Patients get either no pacing or biventricular pacing for 3 months. Then they get the other option for 3 months.
Both studies are ongoing and study biventricular pacing in high-risk CHF patients.
Title: Biventricular pacing in patients with congestive heart failure: two prospective randomized trials. The VIGOR CHF and VENTAK CHF Investigators
Authors: Saxon LA, Boehmer JP, Hummel J, Kacet S, De Marco T, Naccarelli G, Daoud E
Source: Am J Cardiol 1999 Mar 11;83(5B):120D-123D
PMID: 10089853, UI: 99189723
May 15, 1999 - The PATH-CHF group has announced an early end to their trial. They were testing the benefit of pacemakers for patients with moderate to severe heart failure. PATH-CHF is the first study of CHF patients with severe symptoms that has shown big improvements in symptoms after pacemaker implant. The pacemaker coordinates the beating of the heart's chambers.
Pacemaker software was developed just for this trial by the manufacturer, who sponsored the trial. There was immediate improvement of patient symptoms, especially in longer exercise time - by more than 20% of the pre-pacemaker time. Of the 42 patients implanted with a pacemaker, only one patient died from progressive heart failure over a one year follow-up.
The main researcher is Dr. Angelo Auricchio, who enrolled the first patient into the study in 1995. According to Dr. Auricchio, almost all patients in the study improved a lot in both well-being and exercise capacity. Several were scheduled for heart transplant due to severe symptoms, but after implant they were removed from the transplant list due to improved condition.
Title: Multisite Pacing: A New Hope for Patients with Congestive Heart Failure
Author: Dr. Angelo Auricchio
Source: Annual meeting of the North American Society for Pacing and Electrophysiology
January 18, 2001 - Medtronic has announced the start of a new heart failure study. The study is called the "Cardiac Resynchronization - Heart Failure" (CARE-HF) trial, and will enroll 800 CHF patients in Europe. Lasting 18 months, the effect of implanted VRT devices will be tested. Results will report on hospitalization, death, and quality of life.
This trial will enroll patients who do not need the device implanted to stay alive. These CHF patients will be studied to see whether the implanted devices help their life quality and survival when combined with standard drug therapy. All patients will be heart class 3 or 4. Half the patients (400) will get a VRT pacemaker while continuing to take their regular CHF drug therapy. The other half will take drug therapy but won't get a pacemaker. Patients will be followed for at least 18 months.
The trial committee says that other studies show some effectiveness of VRT. However, directly comparing drug therapy alone to drug-plus-device therapy will show how much good it really does. Patients with heart block will probably benefit the most.
"The 400 patients getting a pacemaker will use one of 2 systems, with Medtronic's Attain left-heart leads. Implanted under the skin in the chest area, the InSync pacemaker sends electrical impulses through 2 insulated wires called leads. The leads are threaded through veins into the right upper and the right lower heart chambers. A third wire is maneuvered through a vein to a spot near the left ventricle. The device is in trials in the USA.
The InSync III system allows doctors to control the beating action of the right and left sides of the heart independently. It also monitors heart rate and activity level. Data from CARE-HF and other European studies will add to knowledge gained in the USA-Canadian MIRACLE study of 300 patients.
Source: Medtronic, Inc
March 1, 1999 - Guidant has announced the start of a clinical trial to study their "Contak CD" CHF device with "Easytrak" lead system. This implanted system paces both both sides of the heart like the InSynch pacer but also cardioverts and defibrillates like an ICD. It is specifically designed for heart failure patients.
Standard pacemakers only pace the heart's right side. They rely on the heart's own electrical system to transfer that pulse to the left side. This system paces both sides. The new system is also easier to implant because of the cath-like system for threading leads into the heart chambers.
The system includes the Contak CD pulse generator, which provides bi-ventricular pacing, and ICD functions; the Easytrak lead, a new "over-the-wire" system for reaching the left side of the heart; and Endotak leads to deliver the pacing and defibrillation. The first patient was implanted February 24, 1999, in Davenport, Iowa.
Source: Guidant press release (www.guidant.com/news/1999/1111.htm)
May 3, 2002 - The FDA has approved a VRT pacemaker that also contains an ICD. Guidant's Contak CD is the first ICD to include heart resynchronization, which makes the heart's pumping chambers work better together as a team.
The Contak CD is for advanced heart failure patients who have symptoms despite best drug therapy and who also need an ICD. Guidant said it will begin selling the new device immediately. The list price will be $44,475 but Guidant will not estimate the cost to patients.
The study - 248 patients were enrolled in a randomized, double-blind study. All of them needed an ICD; all had heart failure symptoms despite aggressive drug treatment; and all had a wide QRS duration. Patients ranged from class 2 to class 4 at study start.
Primary endpoint was all-cause mortality, hospitalization for heart failure, and too-fast heart rate requiring ICD use. Secondary endpoints were ability to function physically and quality of life.
This began as a 3 month crossover study. It was later changed to a 6 month study. A total of 581 patients were finally enrolled. Patients were divided into 2 groups. All patients had the ICD function of their device turned on. One group had their VRT pacemaker turned on while the other group's pacemakers were not turned on (unknown to them).
In stable patients with class 3 to class 4 heart failure, Vo2max improved 1.8 ml/kg/min, and QOL scores improved 10 points after 6 months of pacemaker therapy versus the no-pacemaker group.
Results are based only on the subgroup of 227 patients with stable, class 3 to class 4 heart failure. The FDA approval of the Contak CD system approval is based just on the results in those patients with stable, advanced heart failure.
Source: Associated Press & Guidant press package
May 3, 2002 - The COMPANION trial has been stopped by the monitoring committee because patients getting active treatment improved so much. The study involved 1,600 high-risk patients with moderate to severe heart failure. On EKG, all patients had a QRS interval longer than 120 ms, and P-R intervals greater than 150 ms.
There were 3 patient groups. All patients got maximum drug therapy. One group also got resynchronization therapy with Guidant's Contak TR pacemaker. The third group got resynchronization therapy plus ICD with the Contak CD device on top of drug therapy.
There was a 20% reduction in all-cause mortality and all-cause hospitalization in the pacemaker groups. There was a 40% reduction in all-cause mortality in patients with the pacemaker/ICD unit. The lead investigator was Dr. Michael Bristow.
March 15, 1999 - A recent report suggests long-term benefits of VRT for heart failure patients. VRT uses an implanted pacemaker to pace both lower heart chambers to improve their pumping effectiveness. The study included 103 patients with advanced heart failure and weak heart pumping action.
The report included 12-month results of a study done in Europe and Canada. The results showed that improvements in quality of life, exercise time, and reduced fatigue using the Medtronic InSync system at one month were maintained a year later.
The InSync system is an internal pacemaker that coordinates the beating of the heart's chambers. The system is implanted in the chest, with leads to the right atrium and right ventricle. A third lead is placed near the left ventricle.
Study leader Dr. Daniel Gras said, "We wanted to know if VRT has a sustained good effect on these patients. This system may give long-term improvement for some CHF patients, and thus prevent the need for heart transplant."
"On average, patients said their quality of life was better than at the study's start. Quality of life was measured by having patients fill out a questionnaire about 15 daily activities including household tasks; leisure, work, and outdoor activities. The questionnaire was done before the study and at regular intervals during the the study.
"Patients were in class 3 to class 4 CHF at the beginning of the study," said Dr. Gras. "After 12 months with the InSync system, patients' heart function improved by an average of one heart class. Exercise tolerance also improved," he said.
Other trials are also underway in this area:
Source: ACC 49th Scientific Sessions via Reuters Health
Jon's note: this was a prospective, observational trial with no placebo or control groups involved
May 29, 2000 - Coordinating the heart's contractions using VRT improves blood flow and relieves symptoms in some heart failure patients. Several presentations on the topic were given at the 21st Scientific Sessions of the North American Society of Pacing and Electrophysiology.
VRT uses pacemaker electrodes in both ventricles. After sensing a beat started by the heart's natural pacemaker, the device stimulates contractions in both ventricles. Dr. Stefan Sack measured 6-minute walk distance and quality of life in 18 patients with non-ischemic CHF and 7 patients with ischemic CHF before and after implanting a VRT device. All patients had heart conduction problems.
Both groups improved in walking distance and quality of life. Average 6-minute walk distance improved from 336 meters to 413 meters in non-ischemic CHFers and from 335 meters to 420 meters in ischemic CHFers. Average quality of life scores improved from 53 to 18 in non-ischemic CHFers and from 63 to 37 in ischemic CHFers.
"Although VRT was effective in both patient groups," Dr. Sack said, "I believe the best candidate for VRT is the patient with dilated cardiomyopathy and a wide QRS complex."
In another presentation, Yinghong Yu looked at the degree of synchronization between left and right ventricular beats in 29 CHFers. "Patients with less synchronized contraction are more likely to benefit," she said. Dr. Veerichetty Kadhiresan compared VRT effects to QRS durations in 74 heart failure patients. "Maximum QRS duration will select patients more likely to benefit from VRT," Dr. Kadhiresan concluded. "Benefit was best predicted by a maximum QRS duration of 155ms (milliseconds) on EKG."
Dr. Angelo Auricchio summed it up this way, "If a patient has moderate to severe CHF and is already taking the maximum meds he can tolerate, one of these VRT devices might improve that patient."
Source: Reuters Health
August 29, 2001 - The FDA approved Medtronic's InSync system Tuesday. It's a souped-up pacemaker that makes a struggling heart beat more normally by forcing its main pumping chambers to work together. Dr. David DeLurgio says, "It's not for
every heart failure patient, but some will benefit."
Some heart failure patients have hearts whose main pumping chambers don't beat together as a team. The InSync pacer sends an electrical impulse from a small generator in the chest through 3 wires to the heart. The pulse makes the ventricles pump together properly.
In a study of 579 patients, those using the pacemaker improved. In the 6 minute walk test, patients whose pacemaker was turned on could walk 58 more yards than patients whose pacemaker was turned off. Also, 68% of pacemaker patients had improved quality of life compared with 38% in the comparison group. The study only lasted 6 months and did not measure whether the device prolonged life.
InSync is meant only for advanced CHF patients who are not helped by the best drug therapy. Because InSync is different from standard pacemakers, with an additional wire running into a different part of the heart, the FDA is requiring Medtronic to give cardiologists special training before they can begin implanting the device.
Source: Associated Press
December 19, 2000 - Severe heart failure can be treated with inotropic drugs but these drugs force a weak heart to increase its energy use. In CHFers with left bundle branch block (LBBB), some success has been seen with pacemaker use. This study compared the heart's energy use during pacing to energy use during dobutamine use.
Ten LBBB patients with DCM were studied. All measurements were done in a cath lab. All patients had an EF less than 35%, QRS duration longer than 140ms on EKG, were in normal heart rhythm, and did not have coronary artery disease.
Catheters were used to take the measurements, which included the heart's "squeezing" strength, pulse pressure, heart output, pressure to size relationships, and oxygen use. The patients were studied using LV (left ventricular) pacing, BV (biventricular) pacing, and IV dobutamine separately.
LV (left ventricle only) pacing produced an increase in dP/dt (how efficiently the heart beats) of 43% and an increase in aortic pulse pressure of 4%, while oxygen use went down by 8%. BV pacing increased dP/dt by 39% and aortic pulse pressure by 20%, with oxygen use going down 13%. Seven patients got dobutamine. In these patients, oxygen use went up instead of down, by an average of 42%. Overall heart efficiency increased by 100% with LV pacing compared to 34% with dobutamine.
This study suggests that pacing "stresses" the heart less than IV dobutamine, so pacing's long-term effects may be milder. Patients most likely to benefit from LV pacing for heart failure are those with the most uncoordinated heart beats - heart chambers not working together like a team but out of "synch." A wide QRS duration (150ms or more) on EKG means this is the case.
Improved heart function from pacing does not come from changes in the heart muscle itself but rather from "resynchronization" of heart chambers. Pacing makes the heart's chambers beat as a team again.
Source: Left Ventricular or Biventricular Pacing Improves Cardiac Function at Diminished Energy Cost in Patients With Dilated Cardiomyopathy and Left Bundle-branch Block, Nelson GS, Berger RD, Fetics BJ, et al. Circulation 2000;102:3053-3059
December 3, 2001 - A fiber optic-based pacemaker is now made that lets patients with pacemakers have MRIs.
The wire that connects a pacemaker to the heart can heat up to dangerous temperatures during an MRI, possibly burning the heart itself or causing a rapid heart beat. The new device uses optical fiber instead of wire and delivers its pulses through a laser. It will be the first laser to be implanted in the human body, according to the device's makers.
"This redesign eliminates the MRI safety problem completely," said Michael Weiner, CEO of Biophan Technologies. His company created the new device along with a company run by Wilson Greatbatch, who developed the first working implanted pacemaker in 1960. The implantable version probably won't be available for a couple of years.
"This could be a very significant advance," said Dr. Gabriel Gregoratos, who chairs a committee that writes AHA guidelines for inserting pacemakers. Pacemakers are also used to treat epilepsy and Parkinson's disease, relieve acute pain or to stimulate the spinal cord.
The new device offers "an entirely new range of sensing ability" because the circuits at its fiber tip can measure temperature, pressure and flow, Weiner said.
Source: AP (Associated Press)
January 15, 2002 - The first person to receive an implanted heart pacemaker - Arne Larsson - has died at age 86. He received the first heart pacemaker October 8, 1958. The implant was done to correct a heart condition called Stokes-Adams syndrome, which slows the heart beat. Larsson died after a long illness.
The pacemaker was implanted by Dr. Ake Senning, and was developed by Dr. Rune Elmqvist, a medical device engineer. The pacer used just 2 transistors and was the size of a hockey puck. It returned Larsson's heart to 70 beats per minute and his condition improved immediately. However, the device stopped working after just 5 hours. Senning implanted a second pacemaker and Larsson was out of the hospital in 2 weeks.
The operation sparked an ethics debate on whether mechanical devices should be placed in the human body. Current devices are as small as a half dollar and use computer technology and sensors, containing up to half a million transistors. At the time of his death, Larsson had received 26 pacemakers. He appeared at many clinical meetings and was a spokesman for the pacing industry.
March 5, 2002 - Advisors to the FDA recommend approving an implanted VRT pacemaker that is also an ICD. The Panel voted 6 to 5 in favor of approving Medtronic's InSync ICD. It was not smooth sailing, however.
The device is for patients at risk for sudden cardiac death, who also need VRT for a weak, poorly functioning heart. Last year, the FDA approved the VRT pacemaker alone. If approved by the FDA, the main reason to implant the device would be its ICD function.
The panel's uncertainty focused on the incomplete information submitted by Medtronic. At the time of submission, Medtronic filed quality of life data from only 224 patients out of about 300 patients enrolled at the time. Panel members also questioned if Medtronic properly designed the trial and were concerned about potential device failures.
Concern about device failures focused on the surgical procedure. In 31 cases, the surgeons failed to properly insert the lead wires needed to provide the electrical shock and monitor heart functions. One other concern is that the unit's pacemaker functioning might interfere with its ICD function.
Source: Reuters Health
February 25, 2002 - Fifty-three patients with systolic heart failure and BBB had a biventricular pacemaker implanted. Echocardiograms were done at study start and at 6 and 12 weeks.
There were no changes in heart rate or QRS duration after 12 weeks of pacing. Blood norepinephrine levels stayed the same. After 12 weeks of pacing, left atrium size went down. Left ventricle size also went down but its shape did not improve. Measures of the heart's beating strength improved.
Long-term VRT reverses heart remodeling and improves heart function.
Title: Effects of Long-Term Biventricular Stimulation for Resynchronization on Echocardiographic Measures of Remodeling
Authors: Leslie Saxon, Teresa De Marco, Jill Schafer, Kanu Chatterjee, Uday Kumar, Elyse Foster, for the VIGOR CHF Investigators
From: the Cardiomyopathy and Arrhythmia Research and Education Center, University of California at San Francisco
Source: Circulation. 2002;105:1304
July 2, 2002 - CRT - with either one or both ventricles paced - improves exercise capacity and quality of life. "This is the first randomized study to show that different CRT methods give similar improvement," say the authors. Dr. Angelo Auricchio randomly assigned 41 patients with severe CHF and an appropriate EKG reading to the study's pacemaker schedule:
"Both univentricular and biventricular CRT gave similar outcomes," said Dr. Auricchio. Exercise capacity, heart class, and quality of life improved after one month of treatment.
Whichever mode of pacing gave the best "resynchronization" was continued for another 9 months. At one year from the study's start, Vo2max had increased from 13 to 16 ml/kg/minute. Six minute walk distance increased from 357 to 466 meters. Two thirds of patients improved to heart class one or two. There was also a 50% improvement on quality of life questionnaires.
Dr. Auricchio's group reminds us that implanted device therapy has risk and is hard to do just right. However, they think that technology and training advances will simplify the implant procedure and reduce risks.
Source: J Am Coll Cardiol 2002;39:2026-2033
April 10, 2002 - Where pacemaker leads are placed is important to get the most heart beat coordination in CHFers, say British researchers.
Researchers studied heart failure 18 patients who had enlarged and poorly functioning left ventricles (LV) and also had left bundle branch block. The team used 5 minutes of pacing at various sites in the heart and noted the outcome.
The best LV coordination came from a biventricular pacing site in 5 patients, a LV site in 2 patients, and a right ventricle (RV) site in 7 patients. In the remaining 4 patients, beating was not improved.
Dr. Varma concludes, "It is important to realize that some patients may benefit by the simpler right ventricular pacing, while in others, customizing pacemaker therapy with more or different lead placement may be necessary."
Source: Heart 2002;87:322-328
From: Reuters News
July 11, 2003 - People with pacemakers have high risk for CHF according to a report in the European Heart Journal. Dr. Simon Thackray studied 307 people having routine pacemaker followups. Patients had been on pacing for an average of over 5 years. All patients had a medical history, exam, 6-minute walk test and echo.
EF less than 40% was seen in 31% of patients. Of these, 83 had CHF - 70% of these were class 2, 26% were class 3, and 4% were class 4.
Heart failure was seen more often in patients with single chamber pacers (35%) than in those with a double chamber pacer (18%); and in those with chronic a-fib (42%) compared to those in normal heart rhythm (21%). Less than half the CHF/pacer patients had already had their CHF diagnosed before this study.
Decreasing 6-minute walk distance, history of ischemic heart disease and years of pacing, independently predicted CHF. The researchers believe all pacemaker patients should have routine echos to diagnose CHF as soon as possible when it occurs, since they seem to be at high risk.
Source: Reuters Health
Source: Eur Heart J 2003;24:1143-1152.
Title: The prevalence of heart failure and asymptomatic left ventricular systolic dysfunction in a typical regional pacemaker population.
Authors: Thackray SD, Witte KK, Nikitin NP, Clark AL, Kaye GC, Cleland JG.
September 19, 2002 - "Even in a small group of [end-stage] patients, most will benefit from biventricular pacing," says researcher Dr. Martin Schalij. He studied 40 patients with end-stage CHF. The patients were class 3 or class 4 with EFs under 35%, QRS duration longer than 120 ms, and left bundle branch block.
"All measurements were much better 3 months and and 6 months after study start" the researchers reported. At 6 months:
Source: Am J Cardiol 2002;90:379-383.
2003 - About one in 3 CHFers receiving a CRT pacer don't benefit. Pacemaker implant does have risk and it is expensive, so
selecting patients who will benefit is important. People with uncoordinated beating between right and left heart chambers may be helped most.
The most promising measurement for spotting these patients so far is made by echo. An echo using an EKG as a reference can measure the delay between when blood leaves the pulmonary artery and when it leaves the aorta. Such an echo can also measure the delay between motion in different parts of the heart's wall.
One trial showed that using echo to calculate septal to posterior wall motion delay or SPWMD, predicts long-term improvement in heart function with CRT pacing. This study included 25 class three CHFers with EF under 35%. All patients had normal heart rhythm and had left bundle branch block, with QRS duration over 140 ms.
Before pacer implant, an echo was done. Left heart size and SPWMD were measured. Patients were followed up at one month and again at one year. After one year, left heart size, EF, and mitral valve regurgitation all improved. An SPWMD over 100 ms predicted all patients who responded by better than 15% to CRT pacing. The worse the uncoordinated beating of the heart's chambers, the more EF improved.
This trial suggests that measuring SPWMD by echo can help select CHFers who will get definite improvement from CRT pacing. Also, longer-term results from MIRACLE, MIRACLE ICD, and InSync III trials show that most improvement from CRT pacing shows up within 3 months after device implant, with very little further improvement later on. Improvements do seem to last.
Author: Dr. Ileana Pina.
Source: American Heart Association Scientific Sessions 2003.
May 26, 2006 - Risk of infection from device implants has risen much faster than the number of implants in the past 8 years. The risk grew faster for both ICDs and pacemakers. Researchers studied a database of device-related infections. Their study shows that getting an infection from device implant - whether in the device location or myocarditis - increased risk of death 300%.
Most device implant infections happen in the "pocket" where the device actually goes while almost one in five occur as myocarditis. This study used numbers from 1996 to 2003 in the National Hospital Discharge Survey. In 1996 roughly 160,000 devices were implanted and there were about 4000 infections. By 2003, there were roughly 238,000 implants with nearly 13,000 infections. Hospitalizations for device-related infections rose about twice as fast as number of devices implanted. For unknown reasons, being older or female, or both, lowered risk of infection from implant.
Infections are usually "staph" of one sort or another. Many possible reasons for the higher risk of infection were given but none are certain. What is certain is that device implant, and generator/lead replacements carry a risk of infection and this kind of infection raises risk of death. Something to keep in mind.
Source: Heart Rhythm Society 2006 Scientific Sessions
Presenter: Dr Andrew Voigt
All information on this site is opinion only. All concepts, explanations, trials, and studies have been re-written in plain English and may contain errors. I am not a doctor. Use the reference information at the end of each article to search MedLine for more complete and accurate information. All original copyrights apply. No information on this page should be used by any person to affect their medical, legal, educational, social, or psychological treatment in any way. I am not a doctor. This web site and all its pages, graphics, and content copyright © 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Jon C.