Impact of Myocardial Angiotensin-Converting Enzyme Activity on Coronary Vascular Resistance and Serum Brain Natriuretic Peptide Concentration in Coronary Bypass Surgery

Abstract

Angiotensin-converting enzyme (ACE) inhibitors have cardioprotective effects in animals, but whether that occurs in humans is still controversial. The effect of myocardial ACE activity on coronary vascular resistance during coronary artery bypass surgery and on serum brain natriuretic peptide (BNP) concentration after surgery was studied in myocardial tissue sampled from the right atrium of patients during cardiac surgery (n=20). Tissue enzyme activity (nmol/min per mg protein) was measured using a photometric technique, and the flow rate and pressure upon antegrade infusion of a crystalloid cardioplegic solution was measured for calculating the coronary vascular resistance (mmHg. ml(-1). min(-1)). Serum BNP concentration (pg/ml) was measured on days 0 and 5 after the surgery. Linear regression between tissue ACE activity and coronary vascular resistance (y = 0.46x + 0.56, r=0.85) as well as serum BNP concentration on days 0 (y = 129x + 30, r=0.59) and 5 (y = 347x + 180, r=0.73) after the surgery was significant (x: ACE activity; y: coronary vascular resistance/serum BNP concentration). The results indicate that inhibition of myocardial ACE activity might improve coronary circulation during surgery and hence, cardiac function after surgery.

The Application of Angiotensin Converting Enzyme Inhibitors in Heart Surgery

“…2) after the surgery in spite of satisfactory post-operative course. Although clinical meaning of high level BNP is unclear at this moment [56,58], ACE inhibitor, quinapril, suppressed post operative atrial arrhythmia that occur until discharge of patients [4]. Supporting result of my study, recent large clinical study showed that ACE inhibitor plays a critical role in prevention of atrial fibrillation after the heart operation [59].…”

“…Protective effects of ACE inhibitor against ischemia/reperfusion have been confirmed in left ventricular (LV) function, arrhythmia, and coronary circulation [1,4,[8][9][10][11]. ACE and kininase II are the same enzyme, and ACE inhibitors inhibit not only the generation of angiotensin II but also the degradation of several peptides, including bradykinin [12, 13].…”

“…In uneventful course in heart surgery, it is sometimes difficult to find a significant index, because myocardial damage is too mild to affect indices written above [4]. As more sensitive index of cardiac damage, brain natriuretic peptide (BNP) is widely noticed [56,57].…”

“…As more sensitive index of cardiac damage, brain natriuretic peptide (BNP) is widely noticed [56,57]. In my preliminary clinical study, BNP had a significant correlation with myocardial ACE activity and coronary vascular resistance [4]. BNP keep high level not only on day 0 ( Fig.…”

“…Heart muscle is exposed to global ischemia and following reperfusion, because heart is arrested by cross clamp of ascending aorta and has infusion of cardioplegic solution during surgical procedure. As physicians have shown protective effects of ACE inhibitors in coronary angioplasty [2,3], surgeon are also interested in application of ACE inhibitor to heart surgery [1,[4][5][6].…”