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Biomedical subjects

S J Schang

Publications and source records attributed to S J Schang.

8 recordsLinked to original sources
PubMed1978

Coronary and myocardial metabolic effects of combined glyceryl trinitrate and propranolol administration. Observations in patients with and without coronary disease.

Coronary haemodynamic and metabolic effects of propranolol and glyceryl trinitrate were studied in 12 patients with coronary artery disease and 5 without coronary heart disease, at rest and during tachycardia stress. Propranolol-associated reductions in indices of myocardial oxygen demand, left ventricle work, tension time, and left ventricle oxygen utilisation (LVVO2) were reversed when heart rate was controlled by atrial pacing. Adding glyceryl trinitrate at rest also restored heart rate but decreased the left ventricular work index and tension time index as coronary resistance declined paradoxically. Tachycardia-related increases in tension time index and LVVO2 were unchanged after propranolol, and ischaemia (angina, ST depression, and reduced lactate extraction) was not altered in most of the patients. During tachycardia, the addition of glyceryl trinitrate decreased the tension time index and LVVO2; angina recurred in only 4 patients, and ST depression and lactate extraction improved. Similar haemodynamic changes occurred in the patients with normal coronary arteries. In contrast with propranolol administered alone, propranolol plus glyceryl trinitrate enhances tachycardia tolerance and prevents tachycardia-induced manifestations of ischaemia. This action is attributed to glyceryl trinitrate-associated improvement in the adequacy of myocardial perfusion.

Adult↗
PubMed1977

Effects of propranolol on coronary hemodynamic and metabolic responses to tachycardia stress in patients with and without coronary disease.

To clarify the influence of propranolol-and particularly its heart-rate effects-on myocardial ischemia, coronary hemodynamics and metabolism were studied in 15 patients utilizing a protocol to control heart rate. Ten patients had significant coronary narrowing (CAD) and 5 were normal. Systemic pressure, coronary sinus blood flow (CSBF), left ventricular oxygen utilization (LVVO2), ST Segment depression, and myocardial lactate extraction were measured before and after propranolol (10 mg IV), at rest, during pacing-induced tachycardia stress. Propranolol-related reduction in CSBF and LVVO2 at rest was reversed when heart rate was controlled in both patient groups. Propranolol failed to alter heart-rate threshold, tension-time index (TTI), CSBF, or LVVO2 at angina in the CAD patients. Likewise, ischemic-type ST depression, decreases in lactate extraction, and coronary resistance were unchanged compared to values observed during tachycardia stress before propranolol. In normal coronary patients, propranolol also produced no significant change in LVVO2 or coronary resistance when its heart rate effects were controlled. These data imply that a major coronary and metabolic influence of propranolol relates to changes occurring secondary to its influence on heart rate. Furthermore, this agent's anti-ischemic effect is not prominent during tachycardia stress suggesting that this stress test may be clinically useful in patients taking propranolol.

Adult↗
PubMed1977

Transient asymptomatic S-T segment depression during daily activity.

The significance of asymptomatic episodes of ischemic type S-T segment depression was studied in 20 patients with coronary heart disease. Continuous 10 hour electrocardiographic recordings accompanied by detailed daily diaries of activity and symptoms were obtained periodically during a mean time of 16 months. All patients had ischemic type S-T depression associated with angina pectoris during treadmill exercise. Measurements of heart rate, S-T depression and exercise level at the onset of angina obtained during repeated controlled exercise tests at the start of each study period were compared with the measurements recorded during daily activity. After 2,826 hours of recording, 411 transient epidsodes of ischemic type S-T depression were noted during usual daily activity. Only 101 (25 percent) of these episodes were associated with angina. The remaining episodes were unrelated to other symptoms or to posture. All occurred at heart rates significantly lower than those observed at the onset of angina during exercise testing. Of these episodes of asymptomatic S-T depression, 72 percent occurred only at rest or during very light activity such as slow walking or sitting. Nitroglycerin administered hourly significantly reduced the frequency of these episodes, thus supporting the concept that they represent painless ischemia. Because the episodes of asymptomatic ischemic type S-T depression occurred more frequently than angina during usual daily activity and were evident at heart rates and activity levels well below those expected to evoke ischemia, they may be caused by factors other than those that cause angina.

Activities of Daily Living↗
PubMedDate not supplied

Anomalous coronary artery origin and bicuspid aortic valve.

A patient presenting with signs and symptoms suggesting myocardial ischemia was found to have anomalous origin of his right coronary artery from the left aortic sinus of valsalva associated with a bicuspid aortic valve. Abnormal left ventricular function with anaerobic myocardial metabolism was documented in the absence of significant coronary artery disease or aortic obstruction. The possible relationship of these findings to the coronary artery anomaly and bicuspid aortic valve is considered. The necessity of identification of the origin of the coronary arteries is re-emphasized in the evaluation of patients with bicuspid aortic valves coming to cardiac catheterization. Anomalous origin of a coronary artery is a rare occurrence. The association of this anomaly with a bicuspid aortic valve has not been emphasized and the possible clinical consequences of this combination of malformations have not been described. We recently evaluated a patient with anomalous origin of right coronary artery from the left coronary ostium and a bicuspid aortic valve. A description of these findings follows.

Angiography↗