JUNE
The American
Journal
1976
of CARDIOLOGY@ VOLUME
37
NUMBER 7
CLINICAL
STUDIES
Myocardial Bridging and Milking Effect of the Left Anterior Descending Coronary Artery: Normal Variant or Obstruction?
JACQUES MARTIAL ROBERT IHOR
NOBLE, MD G BOURASSA, PETITCLERC,
DYRDA,
MD,
MD,
FACC
MD
FACC
Montreal, Quebec, Canada
From the Montreal Heart lnsthte and Departments of Medlctne and Radiology, Unlverslty of Montreal Medical School, Montreal, Quebec, Canada This work was supported by the Jean-Louls Levesque Foundatton, Montreal, Quebec, Canada Manuscript accepted November 26, 1975 Address for reprints Martial G Bourassa, MD, Montreal Heart Institute. 5000 East, Belanger St , Montreal, Quebec HlT lC8, Canada
Of 5,250 patients undergoing coronary arteriography over a 5 year period, 27 (0.51 percent) had an intramyocardial segment of the left anterior descending coronary artery producing a milking effect or constriction of the artery during systole. Of these, 11 patients with otherwise normal coronary arteries were studied. Hemodynamic data, coronary sinus blood flow and myocardial lactate extraction were measured during atrial pacing at rates of 120 and 150 beats/min and during a 60 watt supine ergocycle exercise test. The degree of narrowing of the left anterior descending coronary artery during systole was graded 3 (greater than 75 percent), 5 patients; 2 (50 to 75 percent), 4 patients; and 1 (less than 50 percent), 2 patients. Four patients with a grade 3 milking effect had S-T depression in the electrocardiogram indicating anterior wall ischemia and lactate production during pacing at 149 f 2 (mean f standard error of the mean) beats/min. Three patients had severe angina during pacing. Two patients with a grade 2 milking effect had angina-like chest pain and electrocardiographic changes during pacing at 150 beats/min. However, lactate extraction was unchanged during pacing. Two patients with a grade 1 milking effect had no angina and no electrocardiographic or metabolic abnormalities. Coronary sinus blood flow increased significantly with pacing and ergocycle exercise in all patients (rest 116 f 6 ml/min; pacing at 150 beats/min 219 f 27 ml/min; ergocycle exercise 251 f 17 ml/min) (P
The American
Journal
1976
of CARDIOLOGY@ VOLUME
37
NUMBER 7
CLINICAL
STUDIES
Myocardial Bridging and Milking Effect of the Left Anterior Descending Coronary Artery: Normal Variant or Obstruction?
JACQUES MARTIAL ROBERT IHOR
NOBLE, MD G BOURASSA, PETITCLERC,
DYRDA,
MD,
MD,
FACC
MD
FACC
Montreal, Quebec, Canada
From the Montreal Heart lnsthte and Departments of Medlctne and Radiology, Unlverslty of Montreal Medical School, Montreal, Quebec, Canada This work was supported by the Jean-Louls Levesque Foundatton, Montreal, Quebec, Canada Manuscript accepted November 26, 1975 Address for reprints Martial G Bourassa, MD, Montreal Heart Institute. 5000 East, Belanger St , Montreal, Quebec HlT lC8, Canada
Of 5,250 patients undergoing coronary arteriography over a 5 year period, 27 (0.51 percent) had an intramyocardial segment of the left anterior descending coronary artery producing a milking effect or constriction of the artery during systole. Of these, 11 patients with otherwise normal coronary arteries were studied. Hemodynamic data, coronary sinus blood flow and myocardial lactate extraction were measured during atrial pacing at rates of 120 and 150 beats/min and during a 60 watt supine ergocycle exercise test. The degree of narrowing of the left anterior descending coronary artery during systole was graded 3 (greater than 75 percent), 5 patients; 2 (50 to 75 percent), 4 patients; and 1 (less than 50 percent), 2 patients. Four patients with a grade 3 milking effect had S-T depression in the electrocardiogram indicating anterior wall ischemia and lactate production during pacing at 149 f 2 (mean f standard error of the mean) beats/min. Three patients had severe angina during pacing. Two patients with a grade 2 milking effect had angina-like chest pain and electrocardiographic changes during pacing at 150 beats/min. However, lactate extraction was unchanged during pacing. Two patients with a grade 1 milking effect had no angina and no electrocardiographic or metabolic abnormalities. Coronary sinus blood flow increased significantly with pacing and ergocycle exercise in all patients (rest 116 f 6 ml/min; pacing at 150 beats/min 219 f 27 ml/min; ergocycle exercise 251 f 17 ml/min) (P
