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D T Mason

Publications and source records attributed to D T Mason.

At least 217 records · Page 12Linked to original sources
PubMed1978

Analysis of myocardial and total body integral extraction ratios of rubidium-86.

Coronary blood flow (QM) measurement with radiorubidium (Rb) assumes that Rb distributes to the myocardium in proportion to flow. This assumption is correct if the integral myocardial Rb extraction ratio (ERM) equals total body extraction (ERTB). A right-heart-bypass preparation was employed to test the hypothesis that ERM = ERTB and to examine the determinants of Rb extraction. Dogs were anesthetized with pentobarbital, and arterial, coronary venous, and total body venous Rb concentrations were continuously measured for 4 min after injection. We found that ERM (0.56 +/- 0.01) was significantly less than ERTB (0.70 +/- 0.01), P less than 0.01 (n = 29) and concluded that Rb did not distribute in proportion to flow. We do not recommend this method for clinical use. ERM is flow dependent and ERRB is a function of the total cardiac output and the distribution of cardiac output. Before employing Rb in animal experiments, it is recommended that a preliminary study be performed comparing flow measured with Rb to an independent measure of blood flow.

Animals↗
PubMed1978

Hemodynamic evaluation in acute myocardial infarction.

Bedside right heart catheterization in patients with acute myocardial infarction and hemodynamic dysfunction provides a rational basis for therapy aimed at maximizing cardiac performance and limiting infarct size. Readily performed and associated with minimal risk, this diagnostic approach is primarily indicated when myocardial infarction is associated with evidence of hemodynamic dysfunction. It affords precise information on cardiac performance and prognosis, allows identification of specific complications such as ventricular septal defect and acute mitral regurgitation, and is of critical importance in selection of therapy. Hemodynamic monitoring is also essential for safe, effective application of certain forms of treatment such as vasodilator therapy for the failing ventricle.

Acute Disease↗
PubMed1978

Comparison of effects of nitroprusside and prazosin on left ventricular function and the peripheral circulation in chronic refractory congestive heart failure.

We compared cardiocirculatory actions of nitroprusside (NP) to prazosin (PZ) in eleven chronic coronary patients with refractory congestive heart failure. Each drug equally lowered systemic arterial pressures mildly while heart rate was unaltered. NP decline (P less than .001) in left ventricular filling pressure (28 to 17 mm Hg) and rise (P less than .005) in cardiac index (2.20 to 2.96 L/min/m2) were similar to PZ (30 to 17) and (2.08 to 3.00). PZ and NP equally enhanced cardiac efficiency of stroke work and myocardial oxygen consumption index. Total systemic vascular resistance declined (P less than .001) the same with NP and PZ. Forearm vascular resistance (FVR) and venous tone (FVT) diminished equally with NP and PZ. Similar FVR/FVT percent changes of 0.88 and 0.64 with NP and PZ indicated relatively balanced systemic arteriovenous relaxation. Sinze PZ effects persisted six hours with symptomatic improvement, oral PZ is the best vasodilator for long-term use, extending in-hospital NP-like actions to ambulatory heart failure therapy.

Adult↗
PubMed1978

Alterations in ventricular mass and performance induced by exercise training in man evaluated by echocardiography.

Few data are available regarding the effects of exercise training upon cardiac structure and performance in man. We evaluated the echograms of 24 normals before (PRE) and after (POST) 11 weeks of endurance exercise training. Conditioning consisted of a walk-jog-run protocol at 70% maximal heart rate for one hour four days per week. Training reduced heart rate and increased maximal duration and estimated oxygen consumption of treadmill exercise. Compared to PRE, the echogram in the POST training period revealed an increased left ventricular (LV) end-diastolic dimension (EdD), a decreased end-systolic dimension (EsD) and thus an increased stroke volume (EdD3-EsD3) and shortening fraction (EdD-EsD)/EdD). Cardiac output (CO) and peripheral vascular resistance (BP/CO X 80) were identical PRE and POST conditioning. Importantly, an increase in mean fiber shortening velocity was observed POST training as were increases in LV wall thickness, ECG voltage of S in V1 + R in V5, and LV mass. Thus endurance training was accompanied by increases in both LV dimension and mass as well as LV shortening fraction and contraction velocity as observed by echocardiogram.

Adult↗
PubMed1978

Lung ventilation-perfusion scintigraphy in pulmonary embolism. Diagnostic specificity compared to pulmonary angiography.

In 53 patients with possible pulmonary embolism, pulmonary abnormalities of 133Xe ventilation and 99Tcm albumin microsphere perfusion scintigraphy were compared with absence or presence of pulmonary emboli documented by concurrent pulmonary angiography. It was found that patients with combined scintigraphy considered as unlikely for pulmonary embolism (ventilation defect larger than perfusion defect) or indicative of pulmonary embolism (ventilation defect smaller than perfusion defect) provide high diagnostic specificity. Patients with equal ventilation-perfusion abnormalities (possible pulmonary embolism) require further evaluation by pulmonary angiography to ascertain diagnosis. Importantly, diagnostic accuracy, using ventilation-perfusion scintigraphy and the quantified method of evaluation delineated, is preserved in patients with severe congestive heart failure.

Adult↗