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Biomedical subjects

D E Wallis

Publications and source records attributed to D E Wallis.

12 recordsLinked to original sources
PubMed1991

Failure of adjuvant heparin to reduce myocardial ischemia in the early treatment of patients with unstable angina.

Although the efficacy of long-term administration of antithrombotic agents in unstable angina has been established, short-term effects on myocardial ischemia are unknown. A retrospective analysis was performed in 47 patients undergoing three-channel continuous ST segment monitoring as part of a multicenter trial using esmolol in unstable angina, in which 20 patients received a continuous heparin infusion during the initial assessment of chest pain. Concomitant medications included calcium channel blockers, beta-adrenergic blockers, nitrates, and aspirin in the majority of patients. Clinical variables between the heparin and no heparin groups were similar, except for fewer males and fewer total artery occlusions in the heparin group. No significant differences in the incidence or duration of ischemia were found in a 36 +/- 16 hour monitoring period. Forty percent of the heparin group had 35 episodes of ischemia with a mean of 11 +/- 10 minutes per episode and a total ischemic time of 48 +/- 39 minutes per patient with ischemia. Forty-four percent of the no heparin group had 47 episodes of ischemia with a mean of 13 +/- 13 minutes per episode and a total ischemic time of 58 +/- 47 minutes per patient with ischemia. Multiple linear regression analysis to adjust for intergroup differences did not alter the results. Eighty-five percent of all episodes were asymptomatic. Clinical events, such as episodes of chest pain, emergency coronary arteriography, or coronary revascularization, were also similar between groups. Thus the short-term administration of heparin did not alter the incidence or duration of ischemia in patients with unstable angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1991

Radiographic pulmonary abnormalities after different types of cardiac surgery.

One aim of this study was to determine the incidence of new radiographic pulmonary abnormalities during hospitalization after cardiac surgery. Another aim was to determine if such abnormalities are more common among patients who had left internal mammary artery (LIMA) grafting. The predictive value of radiographic abnormalities for clinically important pulmonary morbidity was also determined. The anteroposterior chest radiographs of 152 patients obtained by portable equipment were evaluated to determine the incidence of new postoperative radiographic pulmonary abnormalities such as atelectasis, consolidation, infiltrate, and pleural effusion. Clinically important pulmonary morbidity was defined as a delay in tracheal extubation or discharge from the hospital because of a pulmonary reason. Among the 89 patients who had LIMA grafting and left pleurotomy, there was an 88% incidence of left-sided pulmonary abnormalities; a 73% incidence of left-sided atelectasis; and a 55% incidence of left-sided effusion. Among the 63 patients who had saphenous vein grafting only and/or valvular surgery, the respective incidences were 68%, 54%, and 35%, which were lower (P less than or equal to 0.05) than those in the patients who had LIMA grafting. There was no significant difference in abnormalities between the saphenous vein grafting and the valvular surgery groups. The 35% incidence of left-sided pleural effusion when LIMA grafting and pleurotomy were not performed was unexpectedly high. There was no association between radiographic abnormalities and age, the duration of cardiopulmonary bypass, and the duration of aortic occlusion, indicating that cardiopulmonary bypass was not a primary etiology of these radiographic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Electrocardiographic J waves after resuscitation from cardiac arrest.

A patient was monitored prior to, during, and after cardiac arrest with a Holter monitor and an electrocardiograph. The arrest occurred without any premonitory signs on the ECG. At the onset of the arrest, torsades de pointes ventricular tachycardia occurred, which quickly degenerated into ventricular fibrillation. After a successful second defibrillation, the patient developed Osborn waves, which subsided within a few minutes.

Coronary Artery Bypass↗
PubMed1989

Calcium-channel blockers in the management of essential hypertension.

The calcium-channel blockers have expanded the therapeutic choices of the practicing physician. The recent changes in the recommendations regarding first-line therapy in the treatment of essential hypertension have allowed the use of a variety of different antihypertensive agents to provide safe and effective therapy.

Calcium Channel Blockers↗
PubMed1988

Safety and efficacy of esmolol for unstable angina pectoris.

Esmolol is a rapidly metabolized cardioselective beta-adrenergic blocker that provides steady state beta-adrenergic blockade when administered by continuous intravenous infusion. To determine the efficacy of esmolol in the management of unstable angina, 23 patients with known coronary artery disease, who averaged 3.7 +/- 2.7 daily episodes of chest pain at rest, were randomized to receive either a continuous infusion of esmolol (n = 12) or oral propranolol (n = 11), as an adjunct to concomitant antianginal therapy. Patients with systolic blood pressure less than 110 mm Hg, heart rate less than 60 beats/min or known contraindications to beta blockade were excluded. Esmolol was titrated in a step-wise fashion from 2 to 24 mg/min at 5-minute intervals up to a 30% reduction in heart rate and systolic blood pressure double-product. The propranolol dose was increased every 6 hours by 50 to 100% to achieve a similar reduction in heart rate and blood pressure. When compared with their 24-hour baseline periods, both groups achieved a significant reduction in episodes of chest pain, from 4.6 +/- 3.3 to 1.4 +/- 1.5 in the esmolol group (p less than 0.02) and 2.6 +/- 1.4 to 1.0 +/- 1.5 in the propranolol group (p less than 0.02) during the subsequent study period. The cardiac event rate and incidence of drug side effects were similar between the 2 groups; however, side effects seen with esmolol did not require treatment after drug discontinuation. Thus, maximally tolerated beta blockade is an effective therapy for unstable angina.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1988

Effect of esmolol on the ventricular fibrillation threshold.

The effect of esmolol on the ventricular fibrillation threshold (VFT) was determined in 11 open-chest dogs anesthetized with sodium pentobarbital. Since changes in VFT by antiarrhythmic drugs have been shown to depend on the method used to test vulnerability to fibrillation, two methods were studied. The vulnerable period was scanned with a train of pulses (100 Hz, 4 ms, 20 pulses) in nine experiments and a single pulse (10 ms) in eight experiments. Following control measurements, esmolol was administered as an intravenous bolus of 500 micrograms/kg followed by a continuous infusion of 300 micrograms/kg/min. After 15 min of infusion, the adequacy of beta-blockade was tested by the administration of 0.5 micrograms/kg of isoproterenol. Isoproterenol increased the heart rate by only 18 +/- 2 beats/min following esmolol administration which was significantly less than the control response (79 +/- 7 beats/min, p less than 0.01). Although the VFT measured with the single-pulse technique did not change in response to esmolol (14.1 +/- 1.1 mA vs. 14.3 +/- 1.2 mA), the VFT measured with the train-of-pulses technique significantly increased (3.7 +/- 0.5 mA to 14.5 +/- 2.8 mA, p less than 0.01). Twenty minutes after discontinuing esmolol, the VFT measurements were repeated and did not differ from control values with either technique. The increase in heart rate in response to isoproterenol also returned to control values (80 +/- 6 beats/min). The results suggest that the ability of esmolol to raise VFT as measured by the train-of-pulses technique is due to beta-adrenergic blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1987

The effects of elevated intracranial pressure on the canine electrocardiogram.

Striking electrocardiographic abnormalities have been noted in some patients with central nervous system injury. To study the relationship between the electrocardiogram and intracranial pressure, intracranial pressure was elevated in 14 open chest pentobarbital-anesthetized dogs. The right vagus was stimulated to produce sinus slowing and the right atrium was paced at a constant cycle length fast enough to prevent arrhythmias and maintain heart rate constant (750 msec in 11 dogs and 600 msec in three dogs). In nine dogs, intracranial pressure was sequentially elevated to 100, 150, and 200 mmHg. Systolic arterial blood pressure consistently rose to exceed intracranial pressure (P less than 0.005). At a pressure of 150 and 200 mmHg, mean QT intervals shortened significantly in recorded leads II, X, Y, and Z from 0.01). T wave changes were also noted that consisted of increasing positivity in leads II, X, and Y and increasing negativity in lead Z. To delinate the role of the sympathetic nervous system, an additional five dogs were subjected to an intracranial pressure of 200 mmHg before and after bilateral stellate ganglionectomy and timolol (0.1 mg/kg IV). Elimination of sympathetic influences did not significantly alter the electrocardiographic effects of elevated intracranial pressure. Thus, intracranial hypertension results in significant QT shortening and T wave changes that are not entirely mediated by the sympathetic nervous system.

Animals↗
PubMed1986

Peripartum cardiomyopathy: clinical, hemodynamic, histologic and prognostic characteristics.

Peripartum cardiomyopathy is defined as left ventricular dilation and failure, first developing during the third trimester of pregnancy or in the first 6 months postpartum. In an effort to characterize this syndrome in a middle class population, 14 consecutive patients with peripartum cardiomyopathy underwent a detailed history and physical examination, right heart catheterization, M-mode and two-dimensional echocardiography, radionuclide ventriculography and right ventricular endomyocardial biopsy. These patients were then observed with sequential noninvasive studies to determine prognostic indicators. Eight (57%) of these 14 patients were primiparous and an equal number first presented with heart failure concomitant with or immediately before the onset of labor. When these women were compared with 55 patients with idiopathic dilated cardiomyopathy, only mean age at onset of symptoms (28.7 +/- 5.7 versus 48.2 +/- 13.6 years, p less than 0.001) and symptom duration (4.1 +/- 7.7 versus 19.0 +/- 18.4 months, p less than 0.001) differed between the groups. There was no difference in ventricular arrhythmia, left ventricular chamber size, ejection fraction or hemodynamics. Myocyte histologic findings were similar; however, myocarditis was identified in 29% of patients with peripartum cardiomyopathy and in only 9% of those with idiopathic dilated cardiomyopathy. In all patients with peripartum cardiomyopathy and myocarditis, the myocardial biopsy was performed within 1 week of onset of symptoms. Seven (50%) of the patients with peripartum cardiomyopathy had dramatic improvement within 6 weeks of follow-up, and 6 (43%) died.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Streptococcus MG-intermedius endocarditis.

Subspeciation of penicillin susceptible alpha-hemolytic streptococci is not routinely performed. However, Streptococcus MG-intermedius is an extremely virulent organism in this strep subgroup and is associated with abscess formation. Our patient, who had endocarditis due to this organism, remained chronically ill despite appropriate antibiotic therapy, and had a perforated aneurysm of the sinus of Valsalva with a myocardial abscess that required extensive surgical debridement. Persistent fever in patients with S MG-intermedius endocarditis should warrant further work-up for metastatic or myocardial abscess formation.

Endocarditis, Bacterial↗
PubMed1986

Sustained postischemic cardiodepression following magnesium-diltiazem cardioplegia.

Magnesium-diltiazem cardioplegia was evaluated in the intact, perfused rat heart to determine whether the joint administration of these agents would adversely affect myocardial contractile and high-energy phosphate recovery following intermittent, normothermic global ischemic arrest. Sequential metabolic and functional analyses were performed on isolated perfused rat hearts during each phase of the experimental protocol: control (10 min), normoxic cardioplegia (10 min), intermittent global ischemic arrest (two 15-min periods separated by 2 min infusion of the normoxic cardioplegic perfusate), and normoxic postischemic control reperfusion (60 min). Four different cardioplegic solutions were evaluated: 30 mM KCl, 30 mM KCl with 2 mg diltiazem/liter, 20 mM MgCl2, and 20 mM MgCl2 with 2 mg diltiazem/liter. Myocardial phosphatic metabolite levels and intracellular pH were analyzed nondestructively in the intact hearts by phosphorus-31 NMR spectroscopy. Corresponding measurements of peak left intraventricular pressure, rate of peak pressure development (dP/dt), and contraction frequency were performed at the midpoint during each 5-min interval of 31P NMR signal averaging. Magnesium plus diltiazem-treated hearts were distinguished from all other groups by a marked delay in postischemic functional recovery consisting of a prolonged depression in contractility (34% of control, P less than 0.01) that persisted throughout the first 50 min of postischemic reperfusion. Diltiazem in combination with magnesium cardioplegia was detrimental to postischemic functional recovery, despite a rapid restoration of high-energy phosphate stores. The apparent adverse interactive effects of excess magnesium and diltiazem suggest that elective ischemic arrest with magnesium cardioplegia in combination with diltiazem may be contraindicated clinically. The mechanistic basis and drug specificity of this response require further clarification. The present findings appear to exclude ATP and PCr production, and structural causes as the basis for the observed aberrant functional recovery from global ischemia of magnesium plus diltiazem-arrested hearts.

Adenosine Triphosphate↗
PubMed1985

Prognosis and treatment of cardiomyopathy and myocarditis.

Dilated cardiomyopathy is a heterogeneous group of disorders with a prognosis that is dependent upon the severity of presenting clinical and hemodynamic abnormalities. Although this condition is characterized by a high mortality, spontaneous improvement is noted in 25% of cases. Standard therapeutic modalities are nonspecific and consist of the therapy of congestive heart failure and ventricular arrhythmia. Recent studies suggest that beta blockade and cardiac transplantation may soon become accepted modalities in this condition. Acute viral myocarditis is a common disease that has a good prognosis, however occasionally progression to chronic myocardial disease has been identified. The therapy of acute viral myocarditis should be limited to symptomatic treatment, anti-coagulation, and bed rest. When chronic myocarditis is identified on endomyocardial biopsy in patients with heart failure of unknown cause, the treatment differs little from that of dilated cardiomyopathy with the exception that recognizing that efficacy has not been proven; immunosuppressive therapy may be added in life-threatening situations. Future studies will be directed at further clarification of the prognosis of each of these conditions with intensive evaluation of the role of beta blockade and immunosuppression.

Acute Disease↗