Search PubMed⌕ Search

Biomedical subjects

D T Mason

Publications and source records attributed to D T Mason.

At least 145 records · Page 8Linked to original sources
PubMed1981

Therapeutic application of prazosin in chronic refractory congestive heart failure. Tolerance and "tachyphylaxis" in perspective.

The cardiocirculatory actions on the oral vasodilator prazosin were evaluated by cardiac catheterization, forearm plethysmography, echocardiography, treadmill exercise and symptoms in patients with advanced long-standing congestive heart failure. The administration of oral prazosin (2 to 7 mg) reduced forearm venous tone and forearm vascular resistance. Concomitantly, mean systemic arterial pressure and left ventricular filling pressure decreased, and the cardiac index increased. These effects of a single dose of prazosin on left ventricular function were rapid in onset, maximal at 1 hour and sustained for the entire 6-hour period of observation. After two weeks of outpatient therapy with 2 to 7 mg of prazosin four times daily, echographic end-diastolic dimension decreased, whereas the duration of treadmill exercise increased. Symptoms (dyspnea, fatigue, angina) were diminished throughout the course of prazosin therapy, and there was an improvement in the New York Heart Association functional class from 3.7 to 2.2. Thus, prazosin possesses sustained nitroprusside-like balanced dilator actions of the systemic arterial and venous beds, which are effectively translated into the beneficial hemodynamic effects of augmenting cardiac output and relieving excessive left ventricular end-diastolic pressure. The delayed vasodilator tolerance that occurs in 30 percent of the patients is prevented by the prior use of aldosterone antagonists and is easily treated when present. Subacute hemodynamic suppression of beneficial prazosin vasodilator actions is transient and does not preclude successful sustained prazosin therapy of severe heart failure.

Administration, Oral↗
PubMed1981

Short- and long-term therapy of mild essential hypertension with timolol.

The short and long-term antihypertensive action of timolol, a beta blocker, was assessed in 36 mild hypertensives in a 32-wk, double-blind, placebo-controlled study followed by an additional 96 wk of timolol in 17 responders. Diastolic blood pressure (DBP) and heart rate (HR) declined during the first phase from 103 to 93 mm Hg and from 73 to 61 bpm (P less than 0.01) but there was long-term timolol subjects (DBP 89 mm Hg at 32 wk and 88 mm Hg at 96 wk [NS] and HR 62 and 65 bpm [NS]). Although stimulated plasma renin activity in the entire group decreased from 1.08 to 0.28 ng/ml/hr (P less than 0.001), blood pressure reduction did not correlate with this decline (r = 0.29) or with serum timolol level (r = 0.29). In 20 patients who underwent treadmill was not altered. Thus, timolol is effective in reducing mild high blood pressure during short-term therapy and in maintaining this effect over the long term in responsive subjects. It is therefore potentially useful in chronic essential hypertension.

Adult↗
PubMed1981

Hemodynamic effects of morphine and nalbuphine in acute myocardial infarction.

Hemodynamic effects of morphine and the new narcotic analgesic, nalbuphine, were compared in a randomized, double-blind study in 15 patients with acute myocardial infarction (11 men and four women, average age 56.2 yr) and normal group mean hemodynamic function. During a 1-hr evaluation the hemodynamic effects were small but there were changes in several parameters. Morphine reduced heart rate (78 to 72 bpm, p less than 0.01) and diastolic and mean arterial pressures (69 to 64 mm Hg, p less than 0.05; and 91 to 84 mm Hg, p less than 0.05); nalbuphine was associated with a decrease in heart rate (82 to 72 bpm, p less than 0.01), decrease in cardiac index, which remained within the normal range (3.16 to 2.75 l/min/m(2), p less than 0.01), and an increase in systemic vascular resistance (1,204 to 1,461 dynes . sec . cm(-5), p less than 0.05). Neither drug altered systolic arterial pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, stroke index, stroke work index, or pulmonary vascular resistance. Echocardiographic assessment revealed diminution of left ventricular mean velocity of circumferential fiber shortening after nalbuphine (1.26 to 1.08 circ/sec, p less than 0.05). Both drugs induced small reductions in respiratory rate and arterial pH and increases in PAO2. There were no changes in PaO2. Because of the absence of clinically important deleterious effects on cardiac pump function, nalbuphine merits further investigation as an analgesic in acute myocardial infarction.

Adult↗
PubMed1981

Beneficial effects of prostaglandin E1 on myocardial energetics and pump performance in severe CHF.

To provide more effective vasodilator agents for the therapy of severe left ventricular (LV) failure the cardiocirculatory actions of prostaglandin E1 (PGE1) were evaluated in nine coronary patients. PGE1 infusion modestly decreased mean systemic blood pressure (85 to 76 mm Hg, p less than 0.025) and LV filling pressure (19 to 15 mm Hg, p less than 0.01) while heart rate was unchanged (p less than 0.05). Simultaneously, PGE1 augmented cardiac index from 1.9 to 2.5 1/min/m2 (p less than 0.005), raised stroke index from 28 to 35 ml/beat m2 (p less than 0.01) and increased stroke work index from 26 to 30 g-m/m2 (p less than 0.02). Additionally, total systemic vascular resistance decreased from 1862 to 1282 dynes-sec-cm-5 (p less than 0.02) and double product of heart rate and systolic blood pressure diminished from 9492 to 8278 mm Hg (p less than 0.02) while the effective endocardial perfusion pressure was maintained (p less than 0.05). Concomitantly, forearm vascular resistance fell, forearm blood flow was raised, and forearm venous tone remained unchanged. Thus, our results demonstrate that PGE2 is a potent arteriolar vasodilator with markedly beneficial effects of myocardial energetics and on cardiac function in patients with severe ischemic congestive cardiac failure.

Alprostadil↗
PubMed1981

Hemodynamic effects of oral pirbuterol in chronic severe congestive heart failure.

The achievement of satisfactory ambulatory therapy of severe chronic congestive heart failure may be helped by the development of safe and orally effective cardiotonic agents. Therefore, we evaluated by cardiac catheterization and limb plethysmography the temporal cardiocirculatory responses of the new ingestible beta agonist pirbuterol in 10 coronary heart disease patients with severe congestive heart failure refractory to digitalis and diuretics. After a single oral dose of 0.4 mg/kg, ventricular dysfunction was considerably improved during 6 hours of hemodynamic monitoring. Cardiac index increased from a control of 1.7 l/min/m2 to 2.6 l/min/m2 (p < 0.001) at 1 hour and to 2.4 l/min/m2 (p < 0.005) at 3 hours and was 2.2 l/min/m2 (p < 0.001) at 6 hours; left ventricular filling pressure decreased from a control of 24 mm Hg to 19 mm Hg (p < 0.005) at 1 hour and to 18 mm Hg (p < 0.005) at 3 hours and was 22 mm Hg (p < 0.05) at 6 hours. Concomitantly, the peak increment in heart rate (6 beats/min) was minimal and without ectopy and mean arterial blood pressure decreased only 10 mm Hg. total systemic vascular resistance declined by 887 dyn-sec-cm-5, forearm venodilation occurred and the rate-pressure product was unaltered. Thus, oral pirbuterol provides beneficial hemodynamic effects in patients with severe left ventricular dysfunction and appears potentially useful for long-term management of low-output congestive heart failure.

Adult↗
PubMed1981

Angiographic measurement of coronary blood flow by video dilution technique.

A simplified video dilution technique has been developed whereby neither coronary dimensions nor contrast velocity need be measured to obtain coronary blood flow relative to a control flow. In 6 dogs, the distal left anterior descending coronary artery flow was measured by simultaneous electromagnetic flowmeter and video dilution technique. For the 236 paired measurements, the electromagnetic flow ranged from 23 to 196 ml/min for each series. When the first measure of a series was considered the control, the flow ratio difference between electromagnetic and video dilution values had a standard deviation of 12 per cent. When each series was broken into pairs, flow ratio difference between these values had a standard deviation of 10 per cent. Thus, the video dilution technique allows accurate measurement of coronary blood flow relative to a control state, utilizing only the known amount of contrast medium injected and the image from videotape replay of the injection. A patient is presented to illustrate the technique during coronary angiography. Applications include determination of coronary reserve during reactive hyperemia to assess the hemodynamic significance of coronary lesions, and determination of the effects of drugs upon coronary blood flow.

Angina Pectoris↗
PubMed1981

Maturational Changes in Myocardial Contractile State of Newborn Lambs.

There have been no investigations of chronologic changes in postnatal contractile state of both left and right ventricles of the newborn. Thus, we determined isovolumetric indices of contractility in 32 acutely instrumented newborn lambs (1 day to 12 wk; three exteriorized near term fetuses, and four adult sheep. These studies demonstrated a marked increase in inotropic properties of both ventricles which was especially pronounced during the first 3 days of extrauterine life (group 1, left ventricle Vmax 3.2 +/- 0.27 and VCE10 3.2 +/- 0.28 Ml (muscle lengths)/sec; right ventricle Vmax 2.1 +/- 0.2 and VCE10 2.2 +/- 0.13 ML/sec); and was associated with elevated cardiac output (428 +/- 52 cc/kg/min), largely resulting from an elevated stroke volume (2.1 +/- 0.31 cc/kg). During subsequent postnatal maturation, contractility indices of both ventricles gradually declined to values intermediate between newborn and adult ((group IV, 22 to 84 days) - left ventricle Vmax 1.78 +/- 0.13 and VCE10 1.79 +/- 0.15 ML/sec; right ventricle Vmax 1.48 +/- 0.07 and VCE10 1.31 +/- 0.3 ML/sec); associated with a corresponding decline in cardiac output (group IV, 136 +/- 38 cc/kg/min), related in large measure to a decline in stroke volume (0.76 +/- 0.13) cc/kg). Simulation of birth in exteriorized fetuses was associated with a sudden increase in contractile indices for both left (Vmax 2.1 +/- .2 leads to 3.0 +/- .3 and VCE10 2.1 +/- 0.2 leads to 3.1 +/- 0.3 ML/sec) and right (Vmax 2.0 +/- 0.2 leads to 2.5 +/- 0.2 and VCE10 1.9 +/- 0.1 leads to 2.5 +/- ML/sec) ventricles. We conclude that there is a postnatal elevation of ventricular contractile state which contributes to successful postnatal adaptation of the newborn cardiovascular system.

Age Factors↗
PubMed1981

Intra-aortic balloon counterpulsation: rationale, application and results.

Intra-aortic balloon counterpulsation is an effective means of reducing myocardial ischemia and supporting the failing circulation. Its therapeutic benefits are the direct result of distolic augmentation and systolic unloading, the former increasing myocardial perfusion and the latter enhancing cardiac performance. Indirect effect include diminution of ischemia by decrease in the determinants of myocardial oxygen demand and improved ventricular function secondary to the decreased ischemia. Intra-aortic balloon counterpulsation is indicated in clinical syndromes related to intractable cardiac ischemia, including myocardial infarction shock and severe left ventricular failure, refractory ischemic pains, and ventricular arrhythmias unresponsive to medical management. It is also of importance in other situations associated with low cardiac output. This therapeutic modality has recently been considered for early use in extensive myocardial infarction to limit cardiac damage and avert complications. Recent technical advances have facilitated the ease and safety of application of intra-aorta balloon counterpulsation. Complication are of low frequency but can be serious and employment of the method is predicated upon consideration of both potential benefits and risks.

Acute Disease↗
PubMed1980

Cross-sectional echocardiography: physical principles, anatomic planes, limitations and pitfalls.

Although M mode echocardiography has achieved a prominent role in the diagnosis and management of patients with cardiovascular disease, the limited area of view afforded by M mode techniques has restricted the application of ultrasound in many areas. The development of two dimensional echocardiography has obviated many of the limitations inherent in the narrow view of the M mode technique. It has enabled imaging of the heart from additional transducer locations, permitted determination of shape and anatomy and provided the ability to determine motion along two axes. Several types of two dimensional echocardiographs have been developed, and each type offers both advantages and disadvantages. Although two dimensional echocardiography has provided a larger area of view with ultrasound, it has also introduced new limitations including a larger and bulkier transducer, a much reduced sampling rate and a difficult display medium (videotape). In addition, new considerations regarding ultrasonic resolution have been raised. Two dimensional techniques have resulted in new pitfalls in ultrasonic diagnosis related to instrument artifacts as well as to performance and interpretation of the examination. The spurious appearance of cardiac masses because of these ultrasonic artifacts represents a particularly prominent diagnostic pitfall that must be avoided in daily practice. It is anticipated that the new wider field of view provided by two dimensional echocardiography combined with a standard high resolution capability of ultrasound (2 to 4 mm) will result in an increasingly large role for echocardiography in the management of patients with heart disease.

Cardiovascular Diseases↗
PubMed1980

Value and limitations of two dimensional echocardiography in assessment of cardiomyopathy.

Primary myocardial diseases have traditionally been classified into congestive, hypertrophic and restrictive varieties. M mode echocardiography has proved extremely valuable in distinguishing congestive cardiomyopathy with major ventricular dilation and poor contractile performance from hypertrophic cardiomyopathy with predominant left ventricular hypertrophy (septum greater than posterior wall) and normal pump performance, and restrictive disorders with symmetric ventricular wall thickening and normal or diminished contractile function. The contributions of two dimensional echocardiography to the evaluation of patients with congestive or restrictive cardiomyopathy have been limited to certain specific situations, such as the recognition of left ventricular mural thrombi. Twenty-five patients with hypertrophic cardiomyopathy were studied to assess two dimensional echocardiography in the evaluation of patients with this disorder. Two dimensional echocardiography indicated that hypertrophy of the interventricular septum is not uniform from apex to base in all patients but may be greatest in the apical, mid or basal third. In addition, the anterior free wall of the left ventricle was involved in the hypertrophic process in approximately 50 percent of patients. Two dimensional echocardiography documented that the location of systolic anterior motion of the mitral valve in patients with hypertrophic cardiomyopathy is most often at the junction of the mitral valve leaflets and chordae tendineae, although the chordae themselves and even th papillary muscles may be involved in this movement. The heterogeneity of these characteristics may enable patients with hypertrophic cardiomyopathy to be classified into subsets of patients in whom meaningful therapeutic and prognostic implications may be derived. Finally, data derived from two dimensional echocardiography have shown that, although the left ventricle in hypertrophic cardiomyopathy conforms in some degree to the configuration of a catenoid, this geometric conformation is unlikely to account for the genesis of this order.

Cardiomegaly↗
PubMed1980

Effects of oral pentaerythritol tetranitrate in cardiac failure and angina pectoris. Assessment by hemodynamic measurement and exercise capacity.

Oral pentaerythritol tetranitrate produces sustained beneficial hemodynamic effects in patients with cardiac failure of varied etiology. The principle action is a reduction of elevated left ventricular filling pressure. In a small group of angina patients, the oral nitrate in high dosage resulted in considerable increase in angina-limited exercise capacity compared to placebo for four hours following drug administration. No side effects were associated with ingestion of pentaerythritol tetranitrate in these investigations.

Administration, Oral↗