IMPORTANCE OF ATRIOVENTRICULAR SYNCHRONY IN HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY TREATED BY CARDIAC PACING

This study was undertaken to evaluate the effect of permanent dual-cha mber cardiac pacing in hypertrophic obstructive cardiomyopathy resista nt to medication, paying particular attention to atrioventricular sync hrony. Sixteen patients, mean age 59 +/- 13 years (range 36 to 80 year s) were divided into two groups after in initial catheter study perfor med under temporary VDD pacing between March 1990 and April 1993. In g roup I (n = 11), the gradient was decreased by more than 50 % whereas in group II (n = 5), the gradient was-unchanged or reduced by less tha n 50 %. The reduction of the gradient was immediately significant in g roup I, the mean value falling from 104 +/- 33 mmHg (range 60 to 170 m mHg) to 25 +/- 13 mmHg (range 10 to 60 mmHg) (p < 0.0001). In group II , the gradient only decreased initially from 132 +/- 13 mmHg (range 12 0 to 150 mmHg) to 88 +/- 25 mmHg (range 50 to 130 mmHg) (p < 0.003) bu t improved atrioventricular synchrony, obtained secondarily either by pharmacological prolongation of the PR interval (association of betabl ocker and verapamil) or by ablation of the atrioventricular junction, improved the haemodynamic benefits. The residual gradient recorded on the 7th day was only 26 +/- 15 mmHg (range 10 to 50 mmHg) (p < 0.0001) . The comparison of the two populations showed that the mean PR interv al was shorter in group II (p < 0.016) and the mean value of the optim al AV Delay (the longest AV Delay with complete ventricular capture) w as also lower (p = 0.001). The haemodynamic improvement, which tended to increase over the 6 moths follow-up period, was associated with a s ignificant symptomatic benefit, the NYHA functional class status decre asing from 3.2 +/- 0.4 (range 2 to 4) to 1.2 +/- 0.4 (range 1 to 2) (p < 0.0001), the results being indentical in the two groups. Moreover, cardiac pacing was associated with a reduction in mitral regurgitation in 6 patients, with a spectacular regression from stage 4 to stage 1 in one case. The authors conclude that DDD pacing provides sustained h aemodynamic benefits in hypertrophic obstructive cardiomyopathy resist ant to medical treatment, the best results being obtained only after p articularly detailed and individualised programming, sometimes associa ted with a therapeutic intervention to optimize atrioventricular synch rony.