Atrioventricular synchronous pacing in hypertrophic obstructive cardiomyopathy

Abstract: Atrioventricular synchronous pacing in hypertrophic obstructivecardiomyopathy Fredrik Gadler Department of Cardiology, Karolinska hospital, Stockholm, Sweden The study addresses major issues of cardiac pacing in hypertrophic obstructivecardiomyopathy (HOCM). The influence of ventricular pacing site and atrioventncular(AV)-delay on left ventricular outflow tract (LVOT) gradient. The long-term effectsof pacing in HOCM patients with provocable LVOT obstruction only and radiofrequencymodification of AV-conduction as adjunct therapy to optimise pacing. Furthermorethe influence of pacing on septal structure and any lasting effects of pacing followingcessation of pacing and the impact of long-term pacing on quality of life in HOCMpatients. Measurements were made in 15 patients of LVOT gradient and cardiac output at anumber of AV-delays during septal and apical right ventricular stimulation and sinusrhythm. Apical stimulation reduced the LVOT > 30% in all subjects whereas septalstimulation reduced LVOT gradient in only three subjects. Cardiac output did notdiffer between conditions. These data support that an apical stimulation site isof crucial importance for successful pacing in HOCM. A comparison between 19 patients with provocable LVOT gradient only and 22 subjectswith resting LVOT gradients was made after a pacing duration of at least six months.Symptomatology improved to a comparable extent in both groups in parallel with increasedexercise capacity in the majority of subjects. Thus, patients who only exhibit significantLVOT obstruction during provocation benefit as much from pacemaker treat ment aspatients who already have significant obstruction at rest, both acutely and long-term. Six patients with rapid native AV-conduction and refractory to pacing, due tolack of full apical preexcitation underwent radiofrequency modification of the AV-node.Significant lasting prolongation of AV-conduction and full apical preexcitation wasachieved in five subjects, one subject developed complete AV-block after one month.During one year of follow up a significant decrease in LVOT obstruction and symptomatologywas observed. Thus, radiofrequency modification of AV-conduction enhances effectsof pacing in HOCM patients in whom it is difficult to achieve full apical preexcitation. Ten patients successfully paced for a mean of 19 months were randomised to eitherthree months of continued or discontinued pacing. No patient completed the full threemonths of inactive pacing due to retum of intolerable symptoms in parallel with increasedLVOT obstruction. Pacing does not seem to induce lasting effects after cessation,at least not to a degree positively influencing hemodynamics and symptomatology. Quality of life was studied in 82 patients randomised to each three months ofactive or inactive pacing. After the crossover study, a six month period of preferredpacing mode followed. Seventy-six patients preferred active pacing at the end ofthe crossover period. Active pacing induced profound positive changes in almost allareas of quality of life. Pacing has beneficial effects on hemodynamics as well as quality of life in patientswith hypertrophic obstructive cardiomyopathy also in patients with LVOT gradientduring provocation only. To achieve these effects an apical pacing site with an individualoptimised atrioventricular delay is of crucial importance. Radiofrequency modificationof atrioventricular conduction can be used to enhance effects of pacing. Pacing doesnot seem to induce lasting effects of a magnitude to influence hemodynamics or symptomsafter cessation of pacing. Key words: HOCM, pacing, LVOTobstruction, quality of life ISBN 91-628-2748-0