Key result
Abrupt tachycardia increased early coronary sinus blood flow more in innervated patients than denervated patients (26 vs 8 ml/min), a response blunted by alpha adrenergic blockade.
Why the study?
Does alpha adrenergic blockade with phentolamine alter coronary hemodynamics differently in normally innervated patients compared to cardiac allograft recipients?
Does alpha adrenergic blockade with phentolamine alter coronary hemodynamics differently in normally innervated patients compared to cardiac allograft recipients?
Absolute Event Rate: 26% vs 8%
p-value: p=<0.001
The study demonstrates the presence of basal alpha-adrenergic tone in the human coronary vasculature that is withdrawn by a sudden increase in heart rate.
Alpha blockade augments resting coronary flow only in innervated hearts; leaves open clinical relevance and requires prospective validation.
The effect of alpha adrenergic block-ade on coronary blood flow regulation at rest was studied in 11 normally innervated patients and 8 cardiac allograft recipients by measuring arterial pressure and coronary sinus blood flow by thermodilution before and after alpha adrenergic blockade with phentolamine. Coronary vascular resistance was calculated by using coronary sinus blood flow and mean arterial pressure, and metabolic demand was estimated by the product of systolic arterial pressure and heart rate. In addition, the coronary sinus blood flow response to tachycardia was examined in 9 innervated patients and 12 denervated patients, with measurements repeated after phentolamine in 8 of the 9 innvervated patients and 6 of the 12 denervated patients. There was a 7.3+/-4.4% increase in coronary sinus blood flow in the innervated patients in response to alpha blockade, whereas the transplanted patients had an 8.2+/-1.8% fall in coronary sinus blood flow, despite equivalent changes in rate pressure product. The innervated patients also demonstrated a significantly greater increase in coronary sinus blood flow than did the transplanted patients during the first 5 s of an abrupt increase in heart rate (26+/-4 vs. 8+/-2.5 ml/min, P <0.001). This early response was blunted after alpha adrenergic blockade. We conclude that there is basal alpha adrenergic tone present on the coronary vasculature in man that is withdrawn by a sudden increase in heart rate.
No takes yet. Share an insight, caveat, or question.
Orlick et al. (1978) studied Normally innervated patients and cardiac allograft recipients (n=23). Alpha adrenergic blockade (phentolamine) and rapid atrial pacing vs. Denervated cardiac allograft recipients / Baseline was evaluated on Increase in coronary sinus blood flow during the first 5 seconds of an abrupt increase in heart rate (p=<0.001). Abrupt tachycardia increased early coronary sinus blood flow more in innervated patients than denervated patients (26 vs 8 ml/min), a response blunted by alpha adrenergic blockade.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: