TY - JOUR
T1 - Mechanism of acute mechanical benefit from VDD pacing in hypertrophied heart
T2 - Similarity of responses in hypertrophic cardiomyopathy and hypertensive heart disease
AU - Pak, Peter H.
AU - Maughan, W. Lowell
AU - Baughman, Kenneth L.
AU - Kieval, Robert S.
AU - Kass, David A.
PY - 1998/7/21
Y1 - 1998/7/21
N2 - Background - Dual-chamber pacing can improve symptoms in hypertrophic cardiomyopathy (HCM), but the mechanism remains unclear. We hypothesized that pacing generates discoordinate contraction and a rightward shift of the end- systolic pressure-volume relation (ESPVR) and that benefits from this mechanism do not depend on the presence of resting outflow pressure gradients or obstruction. Methods and Results - Eleven patients with NYHA class III symptoms, 5 with HCM, and 6 with hypertensive hypertrophy and cavity obliteration, were studied by invasive conductance catheter methods. No patient had coronary artery or primary valvular disease. Pressure-volume relations were recorded before and during VDD pacing by use of a short (75- millisecond) PR interval to achieve preexcitation. Left ventricular cavity pressure was simultaneously recorded at basal and apical sites, with pressure at the basal site used to generate the ESPVRs. VDD pacing shifted the ESPVR rightward, increasing end-systolic volume by 45% (range, 17% to 151%; P=0.002). Resting and provokable gradients declined by 20% (range, -56% to +3%) and 30% (range, -65% to -12%), respectively (P<0.05). Preload declined by 3% to 10% because of the short PR interval. Preload-corrected contractility indexes and myocardial workload declined by ≃10% (P<0.001). Diastolic compliance and relaxation time were unchanged. Pacing made apical pressure-volume loops discoordinate, limiting cavity obliteration and reducing distal systolic pressures. Results in both patient groups were similar. Conclusions - VDD pacing shifts the ESPVR rightward in HCM patients with cavity obliteration with or without obstruction, increasing end-systolic volumes and reducing apical cavity compression and cardiac work. These effects likely contribute to reduced metabolic demand and improved symptoms.
AB - Background - Dual-chamber pacing can improve symptoms in hypertrophic cardiomyopathy (HCM), but the mechanism remains unclear. We hypothesized that pacing generates discoordinate contraction and a rightward shift of the end- systolic pressure-volume relation (ESPVR) and that benefits from this mechanism do not depend on the presence of resting outflow pressure gradients or obstruction. Methods and Results - Eleven patients with NYHA class III symptoms, 5 with HCM, and 6 with hypertensive hypertrophy and cavity obliteration, were studied by invasive conductance catheter methods. No patient had coronary artery or primary valvular disease. Pressure-volume relations were recorded before and during VDD pacing by use of a short (75- millisecond) PR interval to achieve preexcitation. Left ventricular cavity pressure was simultaneously recorded at basal and apical sites, with pressure at the basal site used to generate the ESPVRs. VDD pacing shifted the ESPVR rightward, increasing end-systolic volume by 45% (range, 17% to 151%; P=0.002). Resting and provokable gradients declined by 20% (range, -56% to +3%) and 30% (range, -65% to -12%), respectively (P<0.05). Preload declined by 3% to 10% because of the short PR interval. Preload-corrected contractility indexes and myocardial workload declined by ≃10% (P<0.001). Diastolic compliance and relaxation time were unchanged. Pacing made apical pressure-volume loops discoordinate, limiting cavity obliteration and reducing distal systolic pressures. Results in both patient groups were similar. Conclusions - VDD pacing shifts the ESPVR rightward in HCM patients with cavity obliteration with or without obstruction, increasing end-systolic volumes and reducing apical cavity compression and cardiac work. These effects likely contribute to reduced metabolic demand and improved symptoms.
KW - Cardiomyopathy
KW - Hemodynamics
KW - Hypertrophy
KW - Pacing
UR - http://www.scopus.com/inward/record.url?scp=0032555166&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032555166&partnerID=8YFLogxK
U2 - 10.1161/01.CIR.98.3.242
DO - 10.1161/01.CIR.98.3.242
M3 - Article
C2 - 9697824
AN - SCOPUS:0032555166
SN - 0009-7322
VL - 98
SP - 242
EP - 248
JO - Circulation
JF - Circulation
IS - 3
ER -