Adrian Chenzbraun

Magnesium therapy for torsades de pointes

This is the first report of the successful use of magnesium sulfate (MgSO4) in 3 consecutive patients with torsades de pointes (TdP). In 1 patient, TdP was induced by a combination of quinidine and amiodarone, in the second by procainamide, and in the third by an overdose of imipramine. The QT intervals before TdP were 0.70, 0.64 and 0.56 second, respectively. A bolus of 1.0 to 2.0 g MgSO4 25% abolished the TdP in all 3 patients; but in the third patient, because of recurrent TdP, a second bolus of 1.0 g and a continuous 24-hour infusion of 1.0 mg/min were administered, preventing TdP. There was no immediate shortening in the QT interval in any patient after MgSO4. Magnesium can be given safely even in patients with acute myocardial infarction, angina pectoris or systemic hypertension, conditions in which isoproterenol is contraindicated; it can be applied faster than temporary cardiac pacing; and its use for TdP appears worthy of additional trials.

Doppler echocardiographic patterns of left ventricular filling in patients early after acute myocardial infarction

Diastolic function is routinely assessed using Doppler-derived left ventricular (LV) filling patterns. Ratios between peak flow velocities during early filling and atrial contraction (E/A) of less than 1 are considered pathologic and diagnostic of impaired relaxation. Myocardial stiffness can normalize the E/A ratio, and thus, in some clinical settings, a normal E/A ratio may identify patients with high filling pressures. LV filling patterns were studied with Doppler echocardiography in 15 healthy subjects and 38 patients with recent acute myocardial infarction. The results were correlated with clinical and hemodynamic variables. E/A ratio less than 1 was found in 14 patients (37%) and in only 1 control subject; E/A ratio greater than 2 found in 5 patients (13%) and in only 1 control subject; 19 patients (50%) had an apparently normal E/A ratio. No correlation was found between LV filling pattern and ejection fraction or presence of diabetes or arterial hypertension. LV end-diastolic pressures were low to normal in patients with an E/A ratio less than 1 and were usually greater than 15 mm Hg in those with normal or abnormally increased (greater than 2) E/A ratios. Thus, an apparently normal E/A ratio in patients after myocardial infarction may identify those with more severe LV diastolic dysfunction and increased LV filling pressure.

The Peripheral Vascular Response to Exercise Is Impaired in Patients with Risk Factors for Coronary Artery Disease

Background: Abnormal coronary and brachial artery responses have been described in individuals with risk factors for coronary artery disease (CAD). Peripheral arterial tonometry (PAT), a newly developed digital plethysmographic technique was used to assess peripheral vascular response to exercise in healthy controls and individuals with risk factors. Methods and Results: Continuous finger PAT during Bruce protocol exercise test was performed in 30 subjects with risk factors for CAD and 30 healthy individuals. Compared with baseline, the PAT wave amplitude at peak exercise decreased in the subjects but increased in the controls: 83 ± 28% vs. 114 ± 40% respectively, p < 0.01. Conclusions: A different pattern of systemic vascular response to exercise was found in individuals with risk factors for atherosclerosis. Since the vascular behavior in these patients is probably related to endothelial dysfunction, it may be that peripheral arterial tonometry can be used as a simple, readily available technique to assess endothelial function.

Age alone is not a risk factor for left atrial thrombus in atrial fibrillation

Objective: Advanced age is an indication for anticoagulation in patients with atrial fibrillation though it is not clear that elderly patients have a higher prevalence of left atrial thrombus. The purpose of this study was to clarify whether advanced age represents a risk for left atrial thrombus formation irrespective of other clinical variables. Design: Observational study in patients with atrial fibrillation undergoing a transoesophageal echo scan for various clinical indications. Setting: University-affiliated cardiology service in a general hospital. Patients: Results are reported in 381 patients, 257 aged less than 75 years (Gr. A) and 124 aged 75 years or more (Gr. B). Results: Thrombi were detected by TOE in 30 patients (7.9%), 21 from group A and nine from group B (8.1% vs 7.2%, p = NS). No thrombi were detected in patients with lone atrial fibrillation. Among patients with either valvular or nonvalvular atrial fibrillation, left atrial thrombus presence was not related to age or anticoagulation status. Conclusions: In patients with atrial fibrillation, age itself does not predict the presence of left atrial thrombus and the only identifiable risk factor seems to be the existing cardiac pathology.

Impact of Age on the Safety and the Hemodynamic Response Pattern During High Dose Dobutamine Echocardiography

Background: The purpose of the present study was to assess the safety and hemodynamic response of high dose dobutamine echocardiography (DE) in different age groups. DE is frequently used in the diagnosis of coronary artery disease; its safety in very elderly patients is not established, and there are no standards for blood pressure and heart rate response. Methods and Results: The test was performed using up to 50 μg/kg/min in 400 patients: 164 middle‐aged (age < 65 years), 187 elderly (age, 65–79 years), and 49 very elderly (age ≥ 80 years). It was stopped because of side effects in 91 (23%) patients. Serious side effects occurred in 1.5% of the patients. There was a significant (60%± 35%) increase in heart rate, and a modest (10%± 19%) increase in the blood pressure (P <.001). The change in heart rate was similar in the three age groups, but there was a blunting of the blood pressure response with age. Hypotension was related to ischemia only in the very old. Conclusions: High‐dose dobutamine is safe in all age groups. Dobutamine induces mainly a chronotropic and less a hypertensive response. The chronotropic response of the very old is similar with that of younger patients, but the hypertensive response is blunted in this group.