Responses of internal mammary artery graft flow to nitroprusside: a duplex Doppler study in hypertensive hearts
Bosi, S.; Guadagni, C.; Pretolani, M.; Balestra, G.; Bellanti, G.; Coccolini, S.; Picano, E.
Journal of Hypertension 14(8): 999-1004
1996
ISSN/ISBN: 0263-6352 PMID: 8884555 Document Number: 460569
To assess the response of internal mammary artery (IMA) flow of hypertensive hearts to nitroprusside infusion. Fifteen patients were studied with a high-frequency duplex Doppler probe from the supraclavicolar approach. All the patients had undergone coronary artery bypass surgery with an IMA graft into the left anterior descending artery. The investigated patients were normotensives (controls, n = 5) and hypertensive with a normal (group 1, n = 5) or a hypertrophic (group 2, n = 5) left ventricle. Values of the left ventricular mass index were 102 +/- 11 g/m2 in controls, 115 +/- 18 g/m2 in group 1 and 153 +/- 8 g/m2 in group 2. The IMA flow volume was studied at baseline and continuously during nitroprusside infusion. The arterial blood pressure was measured each minute by a cuff sphygmomanometer. In each patient we considered the peak flow volume (percentage increment from baseline) and the flow volume at the end point (the lowest tolerated diastolic blood pressure). Nitroprusside infusion induced a comparable flow-volume increment in controls (38 +/- 27%) and in group 1 (24 +/- 11%). Conversely, the flow-volume increment was trivial in group 2 (6 +/- 6%). At the end point, the flow volume was similar to the baseline value in controls (with diastolic blood pressure 67 +/- 9 mmHg) and in group 1 (diastolic blood pressure 61 +/- 4 mmHg), whereas the flow volume declined significantly from baseline (by 23%) in group 2 at a perfusion pressure of 79 +/- 9 mmHg. Hypertensive patients with a normal left ventricular mass exhibit a coronary flow behaviour similar to that of normotensives in response to a nitroprusside infusion. Conversely, hypertrophic hypertensives show a blunted nitroprusside-induced coronary vasodilator response and are much more vulnerable to coronary flow reductions in the face of hypotension. This dynamic assessment of flow patterns can be obtained non-invasively by duplex Doppler monitoring of IMA graft flow.