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Biomedical subjects

G G Rowe

Publications and source records attributed to G G Rowe.

At least 19 recordsLinked to original sources
PubMed1990

Aspirin and dipyridamole and their limitations in the therapy of coronary artery disease.

We have reviewed some of the voluminous literature on the effects of aspirin combined with dipyridamole on coronary thrombosis. There is clear evidence that aspirin is partially effective in preventing platelet aggregation and subsequent thrombosis in experimental constricted and damaged coronary arteries of dogs. Clinical studies show a clear reduction in myocardial infarction in male human subjects who are given aspirin as therapy for unstable angina, or as prophylaxis in asymptomatic individuals. In many studies aspirin and dipyridamole have been combined and are effective. We have not found dipyridamole to be effective in the dog with coronary artery constriction and find no substantial evidence that it is effective in preventing myocardial infarction in man. Until definitive studies show that combining dipyridamole with aspirin is more effective than aspirin alone, we do not recommend its use for prevention of coronary thrombosis.

Animals↗
PubMed1988

Epinephrine potentiation of in vivo stimuli reverses aspirin inhibition of platelet thrombus formation in stenosed canine coronary arteries.

In 18 anesthetized dogs with a 70% mechanically produced coronary artery stenosis, blood flow measured with an electromagnetic flowmeter showed cyclical reductions in flow due to periodic acute platelet thrombus formation. These were abolished in eight of nine dogs with 2.5 mg/kg of aspirin given intravenously and in nine of nine dogs with 5 mg/kg of aspirin. However in 14 of 18 dogs the cyclical flow reductions were temporarily renewed with the infusion of epinephrine 0.4 microgram/kg/min. Human platelets inhibited with aspirin can be reactivated with physiologic amounts of epinephrine. We postulate that in patients with atherosclerotic stenotic lesions the use of aspirin to inhibit arterial thrombus formation may be less effective when they have elevated catecholamines.

Animals↗
PubMed1979

Phasic changes in human right coronary blood flow before and after repair of aortic insufficiency.

We have shown previously that acute aortic insufficiency in chronically instrumented dogs reverses the normally high ratio of diastolic to systolic coronary blood flow. Phasic blood flow in the dominant right coronary artery was measured directly with an electromagnetic flow meter during surgery in eight patients with severe aortic insufficiency before and after relacement of the aortic valve. Before the insufficiency was eliminated, right coronary flow average 116 +/- 37 ml./minute and the diastolic to systolic flow ratio was 0.88 +/- 17. Mean arterial blood pressure averaged 106 +/- 17 mm. Hg, heart rate 84 +/- 19 beats/minute, and mean diastolic pressure averaged 67 +/- 10 mm. Hg. After the aortic valve was replaced with an average heart rate of 90 +/- 15 and mean blood pressure of 103 +/- 13 mm. Hg, the average right coronary blood flow increased to 180 +/- 40 ml./minute with a D/S ratio of 2.18 +/- 0.8. In all cases the right coronary blood flow increased after the aortic insufficiency was eliminated surgically. Right coronary flow probably increased because of the improved diastolic perfusion pressure and the change from predominantly systolic to diastolic coronary flow.

Aortic Valve Insufficiency↗
PubMed1977

Carpentier ring annuloplasty in severe noncalcific mitral insufficiency.

Sixteen patients have undergone Carpentier ring annuloplasty for severe mitral insufficiency (MI) since 1974. Our criteria were clinical and angiographic evidence of severe noncalcific MI, a dilated mitral anulus, absence of severe subvalvular chordal thickening, and no major loss of leaflet substance. Carpentier annuloplasty has been successful in eliminating MI in every patient except one. There have been no embolic problems and no early or late deaths. From 1971 to 1974, a similar group of 20 patients with the same diagnosis underwent prosthetic valve replacement. Even though all patients were receiving anticoagulant drugs, three had emboli and there were one early and three late deaths. In patients with severe noncalcific MI who meet our criteria, Carpentier ring annuloplasty is preferable to valve replacement, thus eliminating the hazards of a prosthesis and of long-term anticoagulant therapy.

Heart Valve Prosthesis↗
PubMed1977

Asymptomatic left ventricular aneurysm: a sequela of blunt chest trauma.

A routine chest X-ray taken four months after blunt chest trauma revealed a left ventricular aneurysm in a totally asymptomatic patient. At surgery a thin-walled, clot-filled aneurysm was successfully removed. This case demonstrates the need for careful follow-up of all patients sustaining blunt chest trauma even though the initial cardiac evaluation may be negative. Our feeling that all such aneurysms should be treated surgically is further reinforced by our operative findings.

Adult↗
PubMed1977

The acute systemic and coronary hemodynamic effects of acetaldehyde.

Acute coronary and systemic hemodynamic effects of acetaldehyde before and subsequent to beta adrenergic blockade by propranolol were studied in intact anesthetized dogs. Acetaldehyde produces a sympathomimetic effect compatible with catecholamine release as seen by an increase in heart rate, cardiac output, pulmonary and systemic pressures and body oxygen consumption. The marked decrease in coronary vascular resistance and increase in coronary blood flow is blocked to only a minor degree by propranolol, indicating that a major part of its action on the coronary circulation is not due to catecholamine release. Acetaldehyde dilates large coronary vessels and appears to increase collateral blood flow to obstructed arteries, as determined by angiographic study.

Acetaldehyde↗
PubMed1977

The systemic and coronary hemodynamic effects of intracoronary arterial tolazoline (Priscoline).

Intracoronary injection of tolazoline in dogs produces transient coronary vasodilatation with marked reduction in the arteriovenous oxygen difference and little change in myocardial oxygen consumption. At lower doses coronary effects are produced almost exclusively but as the dose increases, systemic cardiovascular changes occur also. No fatalities occurred even with large doses of tolazoline into the coronary arteries of these healthy dogs. Since intraarterial tolazoline is used to improve visualization of vascular beds in other portions of the body, its possible use for coronary arteriography is discussed.

Animals↗
PubMed1977

Hemodynamic effects of controlled degrees of coronary artery stenosis in short-term and long-term studies in dogs.

Coronary and aortic blood flow, aortic and distal coronary blood pressure were measured with electromagnetic flowmeters and pressure gauges in 15 anesthetized dogs with the chest left open. Increasing degrees of known, fixed, partial coronary artery obstruction were applied with concentric plastic cylinders 3 mm. in length and with varying internal diameters. Because these plastic cylinders are radiolucent and can also be permanently implanted, postoperative arteriograms were taken to evaluate the degree of stenosis produced. At necropsy the degree of obstruction was checked by ligating and removing the narrowed vessel and examining a histologic section of a stenosed portion. The reactive hyperemic response to a 20 second complete occlusion was recorded with amounts of obstruction varying from 10 to 90 per cent. The reactive hyperemia began to decrease with an average of 36 +/- 10 per cent stenosis. A pressure gradient of 10 mm. Hg across the obstruction occurred with an average of 57 +/- 8 per cent stenosis. The reactive hyperemic response was abolished with an average of 75 +/- 6 per cent stenosis, and with greater degrees of stenosis the total flow began to decrease below control levels. The phasic coronary flow pattern was also altered with increasing amounts of fixed partial obstruction. As the per cent of stenosis was increased, the ratio of diastolic to systolic coronary flow decreased. When reactive hyperemia was abolished, very little diastolic-to-systolic variation remained.

Animals↗
PubMed1976

Platelet aggregation in partially obstructed vessels and its elimination with aspirin.

In 35 open chest anesthetized dogs coronary and aortic blood flow were measured with electromagnetic flowmeters while aortic and distal coronary blood pressure and an epicardial ECG were recorded. A fixed amount of stenosis (60-80%) was produced in the coronary artery by an externally applied plastic cylinder. In 24 of the 35 dogs the coronary blood flow showed cyclical reductions to near zero, with a sudden spontaneous return to near control levels. During reduced flow the epicardial ECG showed ST-segment depression suggestive of ischemia, and ventricular premature beats were often noted. Six animals died acutely during episodes of reduced flow. After 35 mg/kg of aspirin were given intravenously the cyclical reductions in coronary blood flow were abolished and the in vitro platelet aggregations were reduced from a control of 62.1 +/- 15 units (Born technique) to an average of 23.7 +/- 12 units. Histologic sections of the narrowed coronary artery obtained when coronary flow was reduced show an amorphous mass in the lumen which was thought to be a platelet aggregate. Perhaps a similar process of platelet aggregation occurs in the stenosed coronary arteries in man, producing acute coronary obstruction, ischemia, and sudden death.

Animals↗
PubMed1975

Systemic and coronary haemodynamic effects of ketamine in intact anaesthetized and unanaesthetized dogs.

Ten intact anaesthetized dogs breathing room air spontaneously (Group A) were compared with ten artificially ventilated dogs (Group B). All were given a bolus of ketamine 2 mg/kg followed by a 20-min infusion of ketamine 0.1 mg/kg/min. In Group A, coronary sinus blood flow, measured with a thermodilution flowmeter, increased by 90% while coronary vascular resistance decreased by 28% and coronary sinus oxygen content decreased by 27%. Heart rate increased by 47%, and arterial pressure by 9%. Cardiac output, calculated by the dye dilution method, increased by 29%, while the left ventricular work index decreased by 50%. Minute ventilation rate decreased by 55%. The Group B dogs were studied as described above, except that they were artificially ventilated. The haemodynamic ahanges were less in Group B, possibly because of improved arterial oxygenation. Heart rate increased by 24%, cardiac output by 21% and arterial pressure by 2%. The coronary sinus blood flow increased by 12% while coronary vascular resistance decreased by 11%. Coronary sinus oxygen concentration decreased by 15%. Five unanaesthetized dogs with electromagnetic flowmeter probes chronically implanted on the aorta and circumflex coronary artery, and an indwelling arterial catheter were studied before, during and after the intravenous administration of ketamine 2, 4, and 8 mg/kg. A dose of 8 mg/kg produced increases in cardiac output, heart rate and arterial pressure of 21%, 44% and 24%, respectively, while coronary blood flow increased 47%. We conclude that, in healthy dogs, ketamine produces an increase in heart rate and cardiac work. A significant increase in coronary blood flow appears to be insufficient to meet the metabolic demands of the myocardium, as the coronary sinus oxygen content decreased.

Anesthesia, General↗
PubMed1975

Congenital diverticulum of the right and left ventricles.

An asymptomatic congenital cardiac diverticulum was seen on a routine chest film in a 45-year-old man. Right atrial and left ventricular cineangiography showed that the diverticulum communicated independently with both ventricles. There was no evidence of heart failure, arrhythmia, or mural thrombus, and surgery was not deemed necessary.

Diverticulum↗