Effects of Dual-Chamber Pacing on Regional Myocardial Deformation in Patients With Hypertrophic Obstructive Cardiomyopathy

BACKGROUND: This study examined the effects of dual-chamber pacing (DDD) on regional myocardial deformation, as determined by echocardiographic strain and strain rate (SR) imaging, in patients with hypertrophic obstructive cardiomyopathy (HOCM). METHODS AND RESULTS: Fourteen patients (11 men, 3 women; mean age 55 +/-16 years) who had been on long-term DDD (mean period 7.4 +/- 2.1 years) underwent strain and SR imaging. Before and after DDD, the peak strain (%) and SR (s(-1)) during systole were assessed in 8 segments in 4 left ventricular (LV) walls. With DDD turned on, peak strain and SR were significantly increased in the basal anteroseptal (strain -10.2 +/- 6.8 to -1.0 +/- 6.4, p<0.005; SR -0.76 +/- 0.46 to 0.05 +/- 0.58, p<0.001) and septal segments (strain -11.2 +/- 8.9 to -2.2 +/- 7.7, p<0.005; SR -0.85 +/- 0.54 to -0.19 +/- 0.75, p<0.05), but not in the basal posterior (strain -15.0 +/- 13.0 to -13.4 +/- 9.2, p=NS; SR -1.37 +/- 0.57 to -1.93 +/- 0.65, p=NS) and lateral segments (strain -18.1 +/- 10.2 to -15.7 +/- 5.6, p=NS; SR -1.33 +/- 0.68 to -0.84 +/- 0.88, p=NS). These findings were associated with a modest, but significant, change in the LV pressure gradient (24 +/- 12 mmHg to 14 +/- 7 mmHg, p<0.001). CONCLUSIONS: In patients with HOCM, DDD appeared to produce myocardial lengthening in the basal septum during systole, which may have implications for the mechanism of reducing LV outflow obstruction during DDD.