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Dual-chamber pacing produced modest symptomatic and hemodynamic improvements in patients with hypertrophic cardiomyopathy
Dual-chamber pacing produced modest symptomatic and hemodynamic improvements in patients with hypertrophic cardiomyopathy Nishimura RA. Trusty JM, Hayes DL et al. Dual-chamber pacing f o r hypertrophic cardiomyopathy: a randomized, double-blind, crossover trial. J A m Coll Cardiol 1997; 29:435-441
Objective To evaluate the effects of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy. Design Randomized, double-blind, cross-over trial. Setting Single center in Rochester, MN, USA. Patients 21 patients in normal sinus rhythm with severe symptoms of hypertrophic obstructive cardiomyopathy unresponsive to medical therapy and a resting left ventricular outflow tract gradient > 30 mm Hg on cardiac catheterization. For those with a resting gradient < 50 rnm Hg, a provoked gradient Commentary There have been occasional case reports and small studies claiming that patients with obstructive hypertrophic cardiomyopathy (HCM) derive hemodynamic benefit and functional advantage when paced with a short atrioventricular (AV) delay which is necessary to pre-excite the ventricles and cause an eccentric pattern of contraction that is sufficiently uncoordinated to relieve the LVO obstruction. There is no doubt that short AV delay pacing can reduce the outflow tract gradient in HCM. However, it is far from clear whether symptomatic, functional or prognostac benefit results. Nor is it known which patients will derive the most advantage from short AV pacing. Nishimura and colleagues have clearly documented that some patients benefit symptomatically from pacing. They did not show any overall functional improvement and their study was too small and too short to show any prognostic advantage. The short study period might
SEPTEMBER 1997
of> 50 mm Hg was required for inclusion. All patients had to be sufficiently active to perform symptom-limited treadmill exertion tests. Two patients did not complete the study; one undergoing surgical myectomy and one lost to follow-up. The mean age was 58 years (range 35-74) and 53% were men.
Intervention Random allocation in a cross-over fashion to either DDD pacing mode for 3 months or backup AAI pacing mode for 3 months in addition to all usual medications. Main outcome measures Heart rate (HR), systolic blood pressure (SBP), left ventricular outflow (LVO) gradient, Minnesota quality-of-life score (QOL), New York Heart Association (NYHA) class, exercise duration, maximal not have allowed sufficient time for ventricular remodeling that might result from the rehef of outflow obstruction. However, carry-over effects would have potentially compromised the cross-over design if such remodeling had occurred. Several other important studies have been initiated. The European Pacing in Cardiomyopathy (PIC) study is a much larger trial (n = 76) 1utilizing a similar cross-over design and also demonstrated a significant reduction in LVO gradient, general symptomatic improvement but no overall increase in exercise capacity. The American M-PATHY study has yet to report. There is now sufficient evidence to recommend short AV pacing for patients with symptomatic obstructive HCM. The practitioner must make a clinical and echo/Doppler assessment of the results of the pacing intervention. Not infrequently, medication to delay native AV conduction (beta-blockers or non-dihydropridine calcium antagonists) must he
oxygen consumption (VO~ max), and subjective symptomatic response.
Main results There was no change in HR, SBP, NYHA class, and VO 2 max from baseline to either of the two treatment modes. Improvement in subjective symptomatic response over baseline was reported by 63% of patients in the DDD pacing mode and 42% in the backup AAI pacing mode. The mean + standard deviation LVO gradient during DDD pacing was significantly lowered from baseline (54.9 + 38 vs 76.7 + 61 mm Hg; P < 0.05). AAI pacing slightly increased the mean gradient from 76 + 61 mm Hg to 83.4 + 59 mm Hg but was not significantly different from baseline. Mean QOL score was significantly lower (fewer symptoms or limitation of activity) during DDD pacing compared to baseline (P < 0.05) but was not significantly different from A M pacing. Exercise duration during DDD pacing was increased compared to baseline (6.9 vs 5.7 rain; P < 0.05) but was not significantly different from exercise duration during AAI pacing (6.3 rain.) Conclusion Dual-chamber pacing produced modest subjective symptomatic improvement, a modest decrease in the LVO gradient and relief of some symptoms in patients with severely symptomatic hypertrophic obstructive cardiomyopathy. co-administered to ensure pre-excitation of the ventricles. Sometimes radio-frequency AV nodal modification or ablation must be considered. Important questions still remain: does short AV delay pacing result in remodeling of the ventricle and regression of hypertrophy; is a test with temporary pacing leads important to identify those patients who will benefit from pacing; does long-term pacing confer functional and prognostic benefit; is there any indication for pacing in patients with non-obstructive HCM? However, what is certain is that some symptomatic patients with obstruction HCM derive hemodynamic advantage and some report symptomatic improvement from short AV delay pacing. A. John Camm, MD, FACC St George "s Hospital Medical School London, UK Other s o u r c e 1.
K a p p e n b e r g e r L. Personal commumcataon
EVIDENCE-BASED CARDIOVASCULAR MEDICINE
73
Objective To evaluate the effects of dual-chamber pacing in patients with severe symptoms of hypertrophic obstructive cardiomyopathy. Design Randomized, double-blind, cross-over trial. Setting Single center in Rochester, MN, USA. Patients 21 patients in normal sinus rhythm with severe symptoms of hypertrophic obstructive cardiomyopathy unresponsive to medical therapy and a resting left ventricular outflow tract gradient > 30 mm Hg on cardiac catheterization. For those with a resting gradient < 50 rnm Hg, a provoked gradient Commentary There have been occasional case reports and small studies claiming that patients with obstructive hypertrophic cardiomyopathy (HCM) derive hemodynamic benefit and functional advantage when paced with a short atrioventricular (AV) delay which is necessary to pre-excite the ventricles and cause an eccentric pattern of contraction that is sufficiently uncoordinated to relieve the LVO obstruction. There is no doubt that short AV delay pacing can reduce the outflow tract gradient in HCM. However, it is far from clear whether symptomatic, functional or prognostac benefit results. Nor is it known which patients will derive the most advantage from short AV pacing. Nishimura and colleagues have clearly documented that some patients benefit symptomatically from pacing. They did not show any overall functional improvement and their study was too small and too short to show any prognostic advantage. The short study period might
SEPTEMBER 1997
of> 50 mm Hg was required for inclusion. All patients had to be sufficiently active to perform symptom-limited treadmill exertion tests. Two patients did not complete the study; one undergoing surgical myectomy and one lost to follow-up. The mean age was 58 years (range 35-74) and 53% were men.
Intervention Random allocation in a cross-over fashion to either DDD pacing mode for 3 months or backup AAI pacing mode for 3 months in addition to all usual medications. Main outcome measures Heart rate (HR), systolic blood pressure (SBP), left ventricular outflow (LVO) gradient, Minnesota quality-of-life score (QOL), New York Heart Association (NYHA) class, exercise duration, maximal not have allowed sufficient time for ventricular remodeling that might result from the rehef of outflow obstruction. However, carry-over effects would have potentially compromised the cross-over design if such remodeling had occurred. Several other important studies have been initiated. The European Pacing in Cardiomyopathy (PIC) study is a much larger trial (n = 76) 1utilizing a similar cross-over design and also demonstrated a significant reduction in LVO gradient, general symptomatic improvement but no overall increase in exercise capacity. The American M-PATHY study has yet to report. There is now sufficient evidence to recommend short AV pacing for patients with symptomatic obstructive HCM. The practitioner must make a clinical and echo/Doppler assessment of the results of the pacing intervention. Not infrequently, medication to delay native AV conduction (beta-blockers or non-dihydropridine calcium antagonists) must he
oxygen consumption (VO~ max), and subjective symptomatic response.
Main results There was no change in HR, SBP, NYHA class, and VO 2 max from baseline to either of the two treatment modes. Improvement in subjective symptomatic response over baseline was reported by 63% of patients in the DDD pacing mode and 42% in the backup AAI pacing mode. The mean + standard deviation LVO gradient during DDD pacing was significantly lowered from baseline (54.9 + 38 vs 76.7 + 61 mm Hg; P < 0.05). AAI pacing slightly increased the mean gradient from 76 + 61 mm Hg to 83.4 + 59 mm Hg but was not significantly different from baseline. Mean QOL score was significantly lower (fewer symptoms or limitation of activity) during DDD pacing compared to baseline (P < 0.05) but was not significantly different from A M pacing. Exercise duration during DDD pacing was increased compared to baseline (6.9 vs 5.7 rain; P < 0.05) but was not significantly different from exercise duration during AAI pacing (6.3 rain.) Conclusion Dual-chamber pacing produced modest subjective symptomatic improvement, a modest decrease in the LVO gradient and relief of some symptoms in patients with severely symptomatic hypertrophic obstructive cardiomyopathy. co-administered to ensure pre-excitation of the ventricles. Sometimes radio-frequency AV nodal modification or ablation must be considered. Important questions still remain: does short AV delay pacing result in remodeling of the ventricle and regression of hypertrophy; is a test with temporary pacing leads important to identify those patients who will benefit from pacing; does long-term pacing confer functional and prognostic benefit; is there any indication for pacing in patients with non-obstructive HCM? However, what is certain is that some symptomatic patients with obstruction HCM derive hemodynamic advantage and some report symptomatic improvement from short AV delay pacing. A. John Camm, MD, FACC St George "s Hospital Medical School London, UK Other s o u r c e 1.
K a p p e n b e r g e r L. Personal commumcataon
EVIDENCE-BASED CARDIOVASCULAR MEDICINE
73