Effects of dual-chamber pacing in hypertrophic obstructive cardiomyopathy.Immediate results and long term follow-up. A 7-year experience

Background. Sequential pacing as a primary treatment for patients with seve re hypertrophic obstructive cardiomyopathy is still under controversy, In t his study we sought to evaluate the effects of pacing on left ventricular s ystolic and diastolic function, its repercussion on pathophysiology and the possible changes in clinical evolution and functional class in patients wh o didn't respond to medical therapy. Patients and methods. Thirty-four patients with severe hypertrophic obstruc tive cardiomyopathy in functional class III-IV underwent evaluation. The me an age was 64 +/- 11 years. Sixty-two per cent were over 65. The study prot ocol included Holter monitoring, baseline echo-Doppler, during pacing, at 6 months and at the end of followup, and a complete catheterization and coro nary angiography. Mean follow-up time was 36 +/- 20 month (range 6-74). In four patients sequential pacing was ineffective and the protocol had to be discontinued. Thirty patients received a permanent dual-chamber pacemaker a nd systolic and diastolic function were evaluated by hemodynamic, angiograp hic and eco-Doppler studies. Results. Long-term stimulation reduced the subaortic gradient from 95 +/- 3 8 to 39 +/- 28 mmHg (p < 0.001), left ventricular systolic pressure from 20 7 +/- 38 to 164 +/- 30 mmHg (p < 0.001) and left ventricular end-diastolic pressure from 23 +/- 7 to 14 +/- 5 mmHg (p < 0.001), pulmonary capillary we dge pressure from 19 +/- 7 to 14 +/- 5 mmHg (p < 0.001), ejection fraction from 79 +/- 6 to 71 +/- 6% (p < 0.001) and mitral insufficiency. Diastolic function improved with an increase in early filling from 39 +/- 11 to 52 +/ - 10% (p < 0.001) and E/A relation from 0.93 +/- 0.4 to 1.6 +/- 0.8 (p < 0. 001), and a reduction in tate filling from the left ventricle from 36 +/- 1 0% to 24 +/- 10% (p < 0.001). The speed of the E wave increased from 0.83 /- 0.3 to 0.92 +/- 0.3 (p < 0.001) and we observed a reduction of the A wav e from 93 +/- 0.3 to 0.66 +/- 0.2 (p < 0.001), pressure-half time from 95 /- 34 to 66 +/- 19 ms (p < 0.001) and we observed deceleration time from 32 0 +/- 90 to 221 +/- 57 (p < 0.01). All patients have improved their functio nal class, allowing a reduction in pharmacological therapy. Two exitus of c ardiological origin occurred. Conclusions. Sequential AV pacing in selected patients with severe hypertro phic obstructive cardiomyopathy can reduce subaortic gradient, pulmonary ca pillary wedge, left ventricular filling pressures and the severity of mitra l regurgitation, and improve the markedly altered diastolic function. The s ignificant symptomatic improvement allows a reduction in medical treatment. Thus, it represents a viable alternative to open-heart surgery, particular ly in elderly patients, with lower morbidity and mortality rates.