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Biomedical subjects

R MacAlpin

Publications and source records attributed to R MacAlpin.

18 recordsLinked to original sources
PubMed1992

Complete heart block complicating retrograde left-heart catheterization of patients with cardiac allografts.

The development of complete heart block during left-sided cardiac catheterization is an uncommon event. We describe three cases of complete heart block complicating left-sided cardiac catheterization of patients with cardiac allografts. Review of the cases performed at our institution suggests that complete heart block during left-sided catheterization may be more common in patients with cardiac allografts.

Aged↗
PubMed1980

Nifedipine therapy for coronary-artery spasm. Experience in 127 patients.

We report clinical experience with the coronary vasodilator nifedipine in 127 patients with symptoms of myocardial ischemia associated with electrocardiographic or angiographic evidence, or both, of coronary-artery spasm. In the majority of patients conventional antianginal therapy including nitrates and beta-adrenergic blockers failed, and in one third of the patients at least one episode of ventricular tachycardia developed during an attack of angina. Nifedipine (40 to 160 mg every 24 hours) significantly reduced the mean weekly rate of anginal attacks from 16 to two (P less than 0.001). Similar marked reductions in the nitroglycerin requirement were noted. In 63 per cent of the patients complete control of anginal attacks was achieved, and in 87 per cent the frequency of angina was reduced by at least 50 per cent. Nifedipine was generally well tolerated, with only 5 per cent of the patients requiring termination of the drug because of intolerable side effects. This experience with nifedipine suggests that it is a highly effective drug for the treatment of coronary-artery spasm and variant angina.

Adult↗
PubMed1978

Electromagnetic rheoangiometry: an extension of selective angiography.

A harmless magnetic field produced by an extracorporeal magnet induces in the blood vessels of a living subject electrical signals which carry information about regional blood flows. Loop probes of hairlike consistency equipped with fine electrodes can now be introduced percutaneously and selectively into the vasculature through angiographic catheters to pick up these magnetically induced signals at selected loci. In addition to a continuous record of phasic blood flow, the loop sensors provide signals which measure variations in vascular diameters, thus yielding a continuous record of active and passive vasomotion. Coupled with blood pressure recordings, these data will permit determination of the elastic constants of blood vessels in situ. The manifold capabilities of electromagnetic rheoangiometry for providing continuous records of these vascular parameters are illustrated in dogs with tracings using multichannel recorders which provide continuous information of arterial blood pressures, instantaneous and mean blood flows, and instantaneous and mean vascular diameter changes simultaneously in two nonadjacent arteries.

Animals↗
PubMed1977

Effect on training on myocardial oxygen supply/demand balance.

In five well-trained and five sedentary control subjects potential subendocardial blood supply was estimated from the diastolic pressure time index (DPTI) and myocardial oxygen demands from the tension time index (TII) during a progressive near-maximal treadmill test. DPTI/TTi was used to assess the effects of training on myocardial oxygen supply/demand balance. DPTI/TTI was significantly higher in trained subjects at rest and comparable workloads. At 6.4 km/hr, 18% grade (maximum for the controls), TTI was significantly lower (4300 +/- 76 vs 4495 +/- 99 mm Hg-sec/min) and DPTI significantly higher (2534 +/- 86 vs 2295 +/- 91 mm Hg-sec/min) in the trained subjects; DPTI/TTI was significantly higher (0.59 +/- .02 vs 0.50 vs .03). At near-maximal heart rates both groups achieved the same supply/demand balance (0.50); however, the trained subjects were working at higher workloads. We conclude that endurance conditioning increases work capacity, reduces myocardial O2 demands, increases potential O2 supply and improves the supply/demand balance at any given submaximal workload which reduces the risk of ischemia.

Adult↗
PubMedDate not supplied

Polypeptide composition and histopathologic changes in endomyocardial biopsies from transplanted human hearts.

Sequential postoperative samples of 43 human right ventricular endomyocardial biopsies from four heart transplant patients were evaluated histopathologically to assess microscopic parameters of rejection. Selected pieces of these myocardial biopsies were weighed and homogenized in low ionic strength buffer containing Triton X-100 to extract and to quantitate cardiac actin. Aliquots of the soluble fractions were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Residual pellets were solubilized and also underwent SDS-PAGE. Electrophoretograms were analyzed densitometrically. Actin from biopsies from transplanted human hearts accounted for approximately 40% of Triton X-100 soluble polypeptides. Actin and myosin heavy chain content in the pellet fractions was unchanged as a function of allograft duration. A polypeptide band resolved between 14,000 and 21,000 daltons in the Triton-soluble fraction of four fresh samples correlated with histopathologic changes of moderate acute allograft rejection. A similar band was noted in 11 frozen endomyocardial biopsy specimens without changes of acute rejection. Small actin differences may be found in the transplanted heart, but they do not correlate with rejection. The presence on SDS-PAGE of the polypeptide band found between 14,000 and 21,000 daltons may correlate with proteolysis of cytoplasmic proteins either from rejection or possibly from autolysis after freezing.

Actinin↗