H. Thomson et al., Forearm vascular responses during semierect dynamic leg exercise in patients following myocardial infarction, HEART VESS, 13(2), 1998, pp. 87-94
We assessed forearm vascular and blood pressure responses to dynamic leg ex
ercise in patients 7 and 28 days postmyocardial infarction. To determine a
possible association between abnormal exercise vascular responses and baror
eflex dysfunction, integrated and carotid baroreflex sensitivity and forear
m vascular responses (during application of subhypotensive lower body negat
ive pressure) were assessed. On day 7, 42 patients were compared with 21 ag
e- and sex-matched controls. All subjects were assessed for (1) forearm vas
cular resistance during semierect exercise, (2) blood pressure measurements
during erect treadmill exercise, and (3) integrated, cardiopulmonary, and
carotid baroreceptor sensitivity. These studies were repeated in 13 patient
s on day 28. Forearm vascular resistance increased during exercise by 36% /- 63% in patients versus 121% +/- 105% in controls (P = 0.0001), and fell
in 15 patients, a response seen in none of the controls. Exercise hypotensi
on was demonstrated in 5 patients, all of whom had abnormal vasodilator vas
cular responses. Those patients with vasodilator responses had a lower left
ventricular ejection fraction (52% +/- 12% vs 62% +/- 9%; P = 0.007), and
lower cardiopulmonary mechanoreceptor sensitivity (-6.6 +/- 3.9 units vs +6
.4 +/- 10.4 units, P = 0.02) than those with constrictor responses, respect
ively. In the 13 patients studied on day 28, the change in forearm vascular
resistance was similar to that observed on day 7 (36% +/- 63% vs 46% +/- 7
3%). Paradoxical vasodilation of forearm vessels during leg exercise is com
mon in patients studied 7 and 28 days postmyocardial infarction, and is ass
ociated with lower left ventricular ejection fraction and abnormal vascular
responses during subhypotensive lower body negative pressure.