EFFECTS OF HEART-RATE ON CORONARY CIRCULATION AND EXTERNAL MECHANICALEFFICIENCY IN ELDERLY HYPERTENSIVE PATIENTS WITH LEFT-VENTRICULAR HYPERTROPHY

Background and hypothesis: Mechanisms of heart failure in elderly hype rtensive patients with hypertrophy have not been studied sufficiently. We hypothesized that impaired increment of coronary blood flow in res ponse to increases in heart rate could be responsible for the occurren ce or aggravation of heart failure. Methods: To test this hypothesis, we measured coronary hemodynamics and lactate balance during basal con ditions and atrial pacing in 21 elderly patients aged greater than or equal to 65 years (mean 74 +/- 6 years) without coronary arterial dise ase: 7 normotensive control patients (Group 1), 7 hypertensive hypertr ophic patients without a history of congestive heart failure (Group 2) , and 7 patients with such history (Group 3). Coronary sinus blood flo w (CSBF) was measured in coronary sinus using a thermodilution cathete r. Results: During basal conditions, heart rate did not differ among t he three groups (67 +/- 3 in Group 1, 65 +/- 11 in Group 2, and 63 +/- 6 beats/min in Group 3). CSBF was significantly higher in the two hyp ertrophic groups than in the control group, but CSBF normalized by lef t ventricular mass was significantly lower in both hypertrophic groups . External mechanical efficiency (EME) obtained as left ventricular wo rk divided by myocardial oxygen consumption did not differ among group s during basal conditions (36 +/- 9% in Group 1, 35 +/- 8% in Group 2, and 29 +/- 9% in Group 3, NS). During atrial pacing to increase heart rate by 25 +/- 5% (lower) and 54 +/- 6% (higher), the increases in CS BF were markedly limited in both hypertrophic groups, and the response in Group 3 was more depressed than that in Group 2. EME did not chang e in the control group or in Group 2, but did decrease to 21 +/- 5% in Group 3 during the higher pacing rate (p < 0.01 vs. basal conditions) . In this group, the relationship between EME and heart rate showed a significant negative correlation (r = -0.56, p = 0.02). Lactate balanc e in coronary sinus blood showed a tendency to production in Group 3 d uring the higher pacing rate, suggesting myocardial ischemia.Conclusio n: These findings suggest that in hypertensive hypertrophic patients w ith a history of heart failure, the coronary circulation system is vul nerable to increasing heart rate. In medical treatment of elderly hype rtensive patients, control of heart rate in addition to blood pressure control should be considered to minimize the occurrence or aggravatio n of heart failure.