Early postoperative myocardial ischemia after coronary artery bypass grafting. Detrimental effects of nitroglycerine infusion.
This study was aimed at assessing the incidence and mechanisms of myocardial ischemia early after coronary artery bypass grafting and the effects of treatment with nitroglycerine. The electrocardiogram of 35 patients (29 males and 6 females, mean age 61 +/- 8 years) with stable angina and multivessel coronary disease, was monitored continuously for 24 hours after uncomplicated coronary artery bypass grafting. Patients were randomized to receive nitroglycerin infusion or placebo. Fourteen of the 35 patients (40%) had 24 transient ischemic episodes (mean duration 11.8 +/- 3.5 min; range 6-20 min with ST segment elevation in 6, ST segment depression in 7 and both ST segment elevation and depression in 1. Seventy-five per cent of the ischemic episodes occurred within the first 6 postoperative hours. The mean ejection fraction prior to surgery and the mean number of stenosed vessels and of the implanted grafts were similar in patients with and without postoperative ischemia (57 +/- 5 vs 57 +/- 6%, p = 0.86; 2.7 +/- 0.5 vs 2.8 +/- 0.4, p = 0.52 and 3.0 +/- 0.9 vs 3.2 +/- 0.7, p = 0.51, respectively) as well as total bypass time and cross-clamp time (123 +/- 38 vs 124 +/- 18 min, p = 0.89 and 67 +/- 20 vs 70 +/- 14 min, p = 0.68, respectively). The values of heart rate and systolic blood pressure at the onset of the ischemic episodes were similar to those recorded 15 min before (103 +/- 16 vs 106 +/- 18 b/min, p = 0.36 and 119 +/- 12 vs 121 +/- 14 mmHg, p = 0.48). Ischemic episodes were recorded in 9 of the 16 patients (56%) randomized to receive nitroglycerine and in 5 only of the 19 patients (26%) randomized to receive placebo (p = 0.05). Thus, transient ischemic episodes occurring early after coronary artery bypass grafting are not preceded by an increase in myocardial oxygen consumption; they appear to be due, therefore, to a primary reduction in coronary blood flow. Treatment with nitroglycerine is associated with a higher prevalence of ischemic episodes, thus suggesting that myocardial ischemia is unlikely to be caused by spasm of large epicardial vessels or grafts. Myocardial ischemia may be caused, instead, by extracorporeal circulation-induced alterations enhanced by the hypotensive effects of nitroglycerine.
Gaspardone
A
A
Divisione di Cardiochirurgia, Università degli Studi Tor Vergata, Roma.
Penta de Peppo
A
A
Pierri
M D
MD
Cirillo
F
F
Tomai
F
F
De Paulis
R
R
Iamele
M
M
Crea
F
F
Gioffrè
P A
PA
Chiariello
L
L
D000368:Aged; D001026:Coronary Artery Bypass; D004562:Electrocardiography; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000139:chemically induced* / Q000503:physiopathology*; D005996:Nitroglycerin / Q000008:administration & dosage / Q000009:adverse effects*; D011184:Postoperative Period
D005996:Nitroglycerin