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Why Does Cardiac Resynchronization Not Always Work?

Jule 15, 2005 - 30% of CHFers getting a CRT pacemaker
(biventricular/3-lead pacer) don't get any better. In this
study, researchers identified 3 predictors of lack of
response to CRT : Ischemic heart disease, severe mitral
valve regurgitation, and a left ventricular end-diastolic
size of 7.5 cm or more.
	Of 197 consecutive patients scheduled to get a CRT
pacemaker, 143 participated in the study. Average age was
68 years and 79% were men. Heart failure was from ischemic
heart disease in 49 patients (34%). Average QRS was 165 ms
and average EF was 27%.
	Nonresponder patients were those who died of CHF,
had heart transplant, or did not increase distance walked
in 6 minutes more than 10% during the study.
	At 6-month follow up, there were 28 nonresponders
(20%). Of these, 2 got heart transplant and 9 died of heart
failure.
	Things that predicted a patient would not improve
with CRT pacing were ischemic heart disease (3 to 1 odds
against improvement), severe mitral valve regurgitation
(3-1/2 to one odds), and left ventricular end-diastolic
size of 7.5 cm or more (3 to one odds).
	Patients with these 3 predictors were only 27%
probable to improve with CRT pacing.

Title:   Predictors of lack of response to resynchronization
         therapy.
Authors: Diaz-Infante E, Mont L, Leal J, Garcia-Bolao I,
         Fernandez-Lozano I, Hernandez-Madrid A, Perez-
         Castellano N, Sitges M, Pavon-Jimenez R, Barba J,
         Cavero MA, Moya JL, Perez-Isla L, Brugada J.
Source:  Am J Cardiol. 2005 Jun 15;95(12):1436-40.
PMID:    15950566.