Related Experiment Videos
Effects of heart rate on coronary circulation and external mechanical efficiency in elderly hypertensive patients
Y Ishibashi1, T Shimada, S Nosaka
1Fourth Department of Internal Medicine, Shimane Medical University, Japan.
Insights
Elderly hypertensive patients with heart hypertrophy show impaired coronary blood flow when heart rate increases. This suggests heart rate control is crucial for managing heart failure in these patients.
Area of Science:
- Cardiology
- Geriatrics
- Cardiovascular Physiology
Background:
- Heart failure mechanisms in elderly hypertensive patients with hypertrophy are not well understood.
- Impaired coronary blood flow response to increased heart rate may contribute to heart failure.
- This study investigates coronary hemodynamics in relation to heart rate in elderly hypertensive patients with left ventricular hypertrophy.
Purpose of the Study:
- To test the hypothesis that impaired coronary blood flow increment in response to increased heart rate contributes to heart failure in elderly hypertensive patients with hypertrophy.
- To compare coronary hemodynamics and myocardial efficiency during basal and paced heart rates across normotensive controls, hypertensive hypertrophic patients without heart failure, and those with a history of heart failure.
Main Methods:
- Coronary sinus blood flow (CSBF) and lactate balance were measured using thermodilution in 21 elderly patients (mean age 74).
- Patients were categorized into three groups: normotensive controls, hypertensive hypertrophic without heart failure, and hypertensive hypertrophic with prior heart failure.
- Coronary hemodynamics were assessed under basal conditions and during atrial pacing to increase heart rate.
Main Results:
- Hypertrophic patients had higher CSBF but lower CSBF normalized by left ventricular mass compared to controls.
- Increases in CSBF during atrial pacing were significantly limited in both hypertrophic groups, more so in patients with a history of heart failure.
- External mechanical efficiency (EME) decreased in patients with prior heart failure during higher pacing rates, correlating negatively with heart rate and suggesting myocardial ischemia.
Conclusions:
- The coronary circulation in elderly hypertensive patients with hypertrophy and heart failure history is vulnerable to increased heart rate.
- Reduced coronary blood flow response to elevated heart rate may precipitate or worsen heart failure.
- Heart rate control, alongside blood pressure management, should be considered in treating elderly hypertensive patients to prevent or manage heart failure.
Background And Hypothesis:
Mechanisms of heart failure in elderly hypertensive patients with hypertrophy have not been studied sufficiently. We hypothesized that impaired increment of coronary blood flow in response to increases in heart rate could be responsible for the occurrence or aggravation of heart failure.
Methods:
To test this hypothesis, we measured coronary hemodynamics and lactate balance during basal conditions and atrial pacing in 21 elderly patients aged > or = 65 years (mean 74 +/- 6 years) without coronary arterial disease: 7 normotensive control patients (Group 1), 7 hypertensive hypertrophic patients without a history of congestive heart failure (Group 2), and 7 patients with such history (Group 3). Coronary sinus blood flow (CSBF) was measured in coronary sinus using a thermodilution catheter.
Results:
During basal conditions, heart rate did not differ among the three groups (67 +/- 3 in Group 1, 65 +/- 11 in Group 2, and 63 +/- 6 beats/ in Group 3). CSBF was significantly higher in the two hypertrophic groups than in the control group, but CSBF normalized by left ventricular mass was significantly lower in both hypertrophic groups. External mechanical efficiency (EME) obtained as left ventricular work divided by myocardial oxygen consumption did not differ among groups 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 CSBF were markedly limited in both hypertrophic groups, and the response in Group 3 was more depressed than that in Group 2. EME did not change 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 balance in coronary sinus blood showed a tendency to production in Group 3 during the higher pacing rate, suggesting myocardial ischemia.
Conclusion:
These findings suggest that in hypertensive hypertrophic patients with a history of heart failure, the coronary circulation system is vulnerable to increasing heart rate. In medical treatment of elderly hypertensive patients, control of heart rate in addition to blood pressure control should be considered to minimize the occurrence or aggravation of heart failure.