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Biomedical subjects

R R Nelson

Publications and source records attributed to R R Nelson.

5 recordsLinked to original sources
PubMed1978

Left and right ventricular dimensions during ventricular fibrillation in the dog.

Ventricular dimensions by surface echocardiography and intraventricular pressures were monitored in 27 dogs before and during ventricular fibrillation (VF) induced by coronary embolization (nine dogs), potassium infusion (nine dogs) and calcium infusion (nine dogs). Left ventricular diameter (LVD) fell by an average of 10.3 mm during the first 30 s after the onset of VF induced by ischemia or potassium and remained smaller than the prefibrillation end-diastolic LVD during the ensuing 10 min. LVD fell during calcium infusion, and after the onset of VF it remained only slightly larger than the preinfusion end-systolic LVD. Right ventricular (RV) diameter increased progressively for the first 2 min during VF an average of 15.9 mm. The failure of LV size to increase during VF was explained by a pressure gradient inhibiting LV filling during the early phase of VF. Despite progressive RV filling, pressure in the more compliant RV remained lower than in the LV, which exhibited reduced compliance during VF. Therefore, cardiac dilation during VF appears to be confined to the RV, and inhibition to LV filling is an important feature of the syndrome.

Animals↗
PubMed1978

The rate-pressure product as an index of myocardial oxygen consumption during exercise in patients with angina pectoris.

In order to evaluate hemodynamic predictors of myocardial oxygen consumption (MVO2), 27 normotensive men with angina pectoris were studied at rest and during a steady state at sympton-tolerated maximal exercise (STME). Myocardial blood flow (MBF) was measured by the nitrous oxide method using gas chromatography. MBF increased by 71% from a resting value of 57.4 +/- 10.2 to 98.3 +/- 15.6 ml/100 g LV/min (P less than 0.001) during STME while MVO2 increased by 81% from a resting value of 6.7 +/- 1.3 to 12.1 +/- 2.8 ml O2/100 g LV/min (P less than 0.001). MVO2 correlated well with heart rate (HR) (r = 0.79), with HR x blood pressure (BP) (r = 0.83), and, adding end-diastolic pressure and peak LV dp/dt as independent variables, slightly improved this correlation (r = .86). Including the ejection period (tension-time index) did not improve the correlation (r = 0.80). Thus, HR and HR x BP, both easily measured hemodynamic variables, are good predictors of MVO2 during exercise in normotensive patients with ischemic heart disease. Including variables reflecting the contractile state of the heart and ventricular volume may further improve the predictability.

Adult↗
PubMed1977

Exercising pulmonary blood flow in mitral stenosis with anomalous pulmonary venous connection.

Exercising pulmonary blood flow was estimated from indicator-dilution curves in a patient with the infrequent combination of rheumatic mitral stenosis and anomalous pulmonary venous connection from the left lung. During supine exercise against progressively increasing external workloads, the proportion of flow to each lung remained nearly constant. The pulmonary vascular resistance was highest in the left lung, which emptied into the low-pressure systemic vein. Although right and left atrial pressures differed markedly during supine exercise, the proportion of pulmonary blood flow shunted to the systemic venous sytem remained essentially unchanged.

Adult↗