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Biomedical subjects

R N MacAlpin

Publications and source records attributed to R N MacAlpin.

At least 19 recordsLinked to original sources
PubMed1988

Early evolution of symptoms and long-term prognosis in variant angina: importance of the functional component of coronary arterial disease.

PURPOSE: Most investigations describing the long-term outcome of large groups of patients with variant angina pectoris have focused on such endpoints as myocardial infarction, coronary artery surgery, and death, and have asked how the risk of these events is related to the severity of existing organic coronary disease. It is also possible to ask what is the relative importance of organic and functional components in causation of symptoms and outcomes, as was done in this study. PATIENTS AND METHODS: The early and long-term clinical course was observed in a group of 80 patients with variant angina and a low prevalence of severe organic coronary disease (diameter stenosis greater than 70 percent of one vessel in 28.3 percent, of two or more vessels in 2.7 percent). Patients were seen at the UCLA Medical Center between July 1963 and June 1985. RESULTS: The following observations were made: Compared with those experiencing a first episode of angina at rest, subjects whose first episode of vasospastic angina occurred during strenuous effort were more likely subsequently to have a positive exercise test result and a more stable but long-term anginal course. A good initial response to vasodilator therapy indicated a likelihood of being alive and symptom-free without an intervening myocardial infarction by five years after diagnosis, which was twice the rate as if initial response to such treatment was poor. The presence or absence of severe coronary artery obstruction as detected by angiography could not be predicted from the nature or severity of angina, the historical presence of effort angina, or the occurrence of a positive result on an exercise test. The existence of severe coronary stenosis in at least one vessel was not associated with an increased incidence of myocardial infarction, cardiac arrest, or death in the first nine years after diagnosis. CONCLUSION: These findings are consistent with the hypothesis that manifestations of ischemic heart disease in these patients were more directly caused by coronary vasospasm than by the degree of organic coronary obstruction seen by coronary arteriography. In addition, the presence of severe organic stenosis in one coronary artery did not appear to be associated with measurably increased adverse effects on clinical course or survival over the first nine years after diagnosis.

Angina Pectoris, Variant↗
PubMed1986

Angiographic determination of disease-produced alterations of vasomotor tone in large coronary arteries.

Quantitative coronary arteriography was done before and after ergonovine and/or nitroglycerin in 24 patients. After nitroglycerin there was an average 18.6 +/- 3.9% increase in diameter of normal vessels over 2 mm in diameter, and a similar 19.3 +/- 8.7% increase in diameter of the same sized, normal appearing segments in subjects with coronary disease. In individual cases the luminal response to the drug was significantly more variable in "normal" segments of diseased vessels than in entirely normal arteries. Twenty-eight of thirty seven coronary stenoses dilated an average of 18 +/- 10.8% (range 3 to 43%) after nitroglycerin. Unequal dilation of stenosis and normal reference segment caused a 10% or greater change in calculated percent diameter stenosis in 16 lesions. Because they dilated less than would be predicted using a hypothetical geometric model to assess vessel reactivity, most of the lesions could be considered hyporeactive. Ergonovine predictably constricted normal coronary vessels in a relatively uniform fashion. Response of diseased arterial segments was more variable in a limited number of observations. Ergonovine partially antagonized the vasodilating effect of subsequently administered nitroglycerin, and larger than average or intracoronary doses of nitroglycerin had to be used to achieve the same degree of dilation seen with smaller doses in the absence of ergonovine. Disease of large coronary arteries focally alters their vasomotor tone and reactivity as gauged by responsiveness to nitroglycerin and ergonovine. Some implications of this are discussed.

Coronary Angiography↗
PubMed1982

Multiclinic controlled trial of diltiazem for Prinzmetal's angina.

To assess the efficacy of a new calcium entry blocker, diltiazem (Cardizem), for prophylaxis of Prinzmetal's angina, 48 patients were studied in randomized, multiple crossover multiclinic study (2 weeks single-blind, 8 weeks double-blind). Diltiazem dosage in one crossover phase was 120 mg per day; in the other, 240 mg per day. Therapeutic response was measured by patients' diary records of angina frequency and nitroglycerin tablet consumption. Treatment with 120 mg of diltiazem per day reduced angina by 41 percent from the entry placebo period and 20 percent from the paired placebo period (p less than 0.005). Treatment with 240 mg of diltiazem per day reduced angina frequency by 68 percent from the entry placebo period and 43 percent from the paired placebo period (p less than 0.01). There were similar reductions in nitroglycerin consumption. Adverse experiences that may have been related to the medication were noted in only 5 percent of patients. There were no alterations in blood pressure or heart rate. The PR interval increased 3 percent at the 240 mg dosage level. We conclude that diltiazem is an effective and safe agent for control of symptoms of Prinzmetal's angina.

Adult↗
PubMed1982

Observations of arterial and venous vasomotion with the absolute induction angiometer.

This paper provides biological illustrations of the applicability and mode of use of intravascular and perivascular absolute induction angiometers. Artifacts and limitations of the method as well as experimental precautions and calibration procedures are discussed. Tracing are presented to illustrate the capabilities of the method in recording pulsatile diameter changes in veins and arteries and to demonstrate its applicability to moving blood vessels as exemplified by the coronary arteries. Both intravascular and perivascular angiometry can detect diameter changes of a few micra in a vessel 1 cm in diameter. The intravascular angiometer is a resilient loop of fine bifilar wire which can be introduced into the blood vessel percutaneously via an angiographic catheter. A perivascular angiometer is an easily deformable loop made of a soft fine wire pair which is draped around a blood vessel and can thus be chronically implanted.

Animals↗
PubMed1980

Relation of coronary arterial spasm to sites of organic stenosis.

Among 63 patients with Prinzmetal's variant angina, coronary arterial spasm responsible for attacks of variant angina was documented arteriographically in 9 patients. In each observed episode (11 attacks in nine patients), coronary spasm producing myocardial ischemia occurred at and was superimposed on a site of preexisting organic stenosis. Measurements of normal portions of "spastic" and "nonspastic" vessels suggested a generalized uniform constriction of all major coronary arteries during attacks, with "spasm" limited to the site of an organic lesion in most cases. In two cases the magnitude of constriction in all vessels was consistent with generalized coronary hypercontractility or spasm. Among 104 patients with organic coronary artery disease and documented single vessel coronary spasm (foregoing 9 patients combined with 95 others from published reports), there were 70 patients with essentially single vessel organic coronary disease in 90 percent of whom the spasm involved the diseased vessel. Of 60 cases abstracted from the literature in which the relation of coronary spasm to the site of organic disease was described, 88 percent had the spasm causing ischemia localized to the site of an organic lesion. Hypotheses attempting to describe the pathophysiologic aspects of coronary spasm in variant angina must account for the intimate association of spasm with sites of organic stenosis in the majority of cases.

Angina Pectoris↗
PubMed1980

Contribution of dynamic vascular wall thickening to luminal narrowing during coronary arterial constriction.

Available estimates of the ratio of wall thickness to luminal radius of human coronary arteries and certain geometrical assumptions were used to calculate the amounts of vascular smooth muscle shortening required to produce specific changes in luminal diameter for hypothetical "normal" and stenotic arteries. The results indicate that even modest mural thickening due to disease may act as a "lever" in translating physiologic degrees of medial smooth muscle shortening into critical luminal obstructions, providing the diseased segment maintains some pliability. The possibility of acute luminal occlusion occurring at stenotic sites as the result of "normal" vasomotion is illustrated. The appropriate use of the term coronary arterial "spasm" is discussed in light of these observations.

Adult↗
PubMed1979

Coronary ostial embolus and mitral vegetation simulating a left atrial myxoma: a case of probable cryptococcal valvulitis.

A 56 year old man died with disseminated cryptococcosis after immunosuppressive therapy for a hematologic disorder of unknown etiology. The immediate cause of death was cardiogenic shock, probably resulting from a large right coronary ostial embolus and subsequent ischemic myocardial injury. The embolus originated from a bulky mitral vegetation (possibly cryptococcal) demonstrated ante mortem by echocardiography and cardiac angiography, and at autopsy. The differential diagnosis of such an echocardiographic pattern is discussed.

Coronary Disease↗
PubMed1978

Differential effects of Pitressin on blood flow and oxygen extraction in canine vascular beds.

Physiologic studies in dogs have been performed with an intravascular flow/diameter sensor which can be introduced directly into the aorta or its branch vessels through a percutaneous radiologic catheter. These studies have focused upon attempts to devise a clinically practical means to protect the small intestine from radiation damage during therapy of abdominal and pelvic malignant tumors. The effects on superior mesenteric, renal, and lower extremity blood flows of controlled infusions of Pitressin given directly into the superior mesenteric artery or into a peripheral vein have been measured. In addition, using these regional flow measurements and arteriovenous differences in oxygen content, regional tissue oxygen extraction rates during Pitressin infusions have also been estimated. The data show that intravenous Pitressin at an infusion rate of 0.0124 U/kg/min may be almost as effective as Pitressin given directly into the superior mesenteric artery in lowering superior mesenteric blood flow (40%-70% reduction for intravenous, 50%-70% for direct arterial infusions) and intestinal oxygen extraction (20%-40% reduction for intravenous, 40%-50% for direct arterial infusions). The effects of Pitressin at similar dose rates on the kidney and the lower extremity are less reproducible, and it is possible that relatively selective radiation protection of the intestine using systemic (intravenous) infusions of Pitressin during abdominopelvic radiotherapy might be achievable.

Animals↗
PubMed1977

The inside-out electrocardiographic stress test: a view from the left ventricular cavity.

A new method is described for measuring the unipolar left ventricular cavitary electrogram by means of a standard pigtail ventriculography catheter. Experiences with this technique in 30 patients are described with particular reference to changes in the S-T segment of the cavitary electrogram during cardiac stress by atrial pacing. This method allows convenient recording of His bundle potentials from the left ventricular outflow tract in most patients.

Angina Pectoris↗