Background: Dual pacing stimulation improves symptoms and reduces intraventricular pressure gradient in obstructive hypertrophic cardiomyopathy. The mechanisms proposed for these effects are a change in ventricular contraction sequence, a paradoxical movement of the interventricular septum and a reduction in ventricular contractility. However, dual chambers pacing stimulation effects on systolic and diastolic function are unknown, and the study of this is the aim of this work.
Patients and methods: We performed a radionuclide ventriculography in 10 patients with obstructive hypertrophic cardiomyopathy at 2 days and 1 and 6 months after placing a dual chamber pacemaker. The phase images, ventricular volumes, left ventricular ejection fraction and segmentary contractility were evaluated. Diastolic maximum peak-filling-rate and time to-peak-filling-rate were also studied.
Results: In DDD pacing stimulation, parametric phase images show a reversal up-down contraction sequence starting from the apical segment. At 6 months radionuclide ventriculography, a reduction in ejection fraction was found (60.9 +/- 12 vs 73.4 +/- 9.1; p < 0.05) which was attributed to apical, apical-septum and mainly basal-septum segmentary contraction decrease. A paradoxical mid-systolic septum movement was also found during DDD stimulation. No differences on diastolic parameters were noted.
Conclusion: During dual chamber stimulation, a reversal ventricular contraction sequence, a paradoxical septum movement, hypokinesis of the septal ventricular segments and a reduction on left ventricular ejection fraction was observed.