Cardiology
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Comparative Study
PVF velocity pattern in patients with heart failure: transesophageal echocardiographic assessment.
In order to assess the role of the pulmonary venous flow (PVF) velocity pattern in the evaluation of patients with congestive heart failure (CHF), we studied 41 CHF patients by means of transthoracic echocardiography (TTE) and multiplane transesophageal echocardiography (TEE). The etiology of CHF was idiopathic or ischemic dilated cardiomyopathy in 19 patients and hypertensive heart disease in 22. Sixteen subjects without cardiovascular disease were selected as normal controls. ⋯ Patients with LVEF < 40% showed mean SF values significantly lower than patients with LVEF > 40% (33.26 +/- 10.84 vs. 51.00 +/- 4.00%, p < 0.0001). Mean DT and LVIRT values were not significantly different in patients with LVEF < 40% and > 40%. Thus in CHF patients TEE PVF velocity patterns help in distinguishing patients with systolic dysfunction (low LVEF and SF) from patients with predominant diastolic impairment (normal or nearly normal LVEF, high D velocities).
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Comparative Study
Doppler echocardiographic assessment of left ventricular diastolic function in myotonic dystrophy.
We utilized Doppler echocardiography to characterize left ventricular diastolic function in 42 patients with myotonic dystrophy (mean age 37 +/- 12 years, 64% male) who had no symptoms of heart failure and had normal left ventricular systolic function. Data were compared with those in 41 normal control subjects of similar age and gender. Heart rate, systemic blood pressure, and cardiac dimensions (wall thickness, left atrial and left ventricular cavity dimensions) were similar and not significantly different in patients and controls. ⋯ During observation no patients died and none experienced symptoms of heart failure. This Doppler echocardiographic analysis demonstrates that diastolic abnormalities may be present in patients with myotonic dystrophy, even in the absence of symptoms of cardiac failure or left ventricular systolic dysfunction. These diastolic abnormalities suggest an intrinsic myocardial abnormality in patients with myotonic dystrophy; however, whether they represent a preclinical phase of myocardial involvement or an intrinsic feature of the primary myocardial disease process in myotonic dystrophy remains to be elucidated.
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Prolonged strenuous exercise may trigger acute myocardial infarction (AMI), as exemplified by the occurrence of sudden cardiac death during marathon running. Serum creatine kinase MB (CK-MB) may be elevated in asymptomatic marathon runners after competition from exertional rhabdomyolysis of skeletal muscle altered by training, limiting its utility for evaluating acute cardiac injury in such athletes. Myoglobin and CK-MB2 isoform levels are emerging as earlier markers of AMI and troponin subunits as more specific than serum CK-MB mass. ⋯ While the mean serum values for cardiac troponins T and I remained normal, 9 of 45 runners (20%) showed an increase in subunits by first-generation assays. All runners remained asymptomatic for cardiac disease and completed subsequent marathons 1 year later, making reversible myocardial injury or stunning unlikely. Elevated values of serum markers for AMI, including first-generation assays for both troponin subunits should be interpreted with caution in trained runners.
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Paroxysmal atrial tachycardia with atrioventricular block usually indicates potentially dangerous overdigitalization, and serious heart disease is almost universally present. In this report, we describe a patient with a structurally normal heart who manifested spontaneously intra-atrial reentrant tachycardia with Wenckebach atrioventricular block in the absence of medications. In this patient, the longest atrial paced cycle length that induced atrioventricular nodal block was 390 ms, and the atrial cycle length during tachycardia ranged from 360 to 400 ms. The electrophysiologic study in our patient demonstrated that second-degree atrioventricular block during atrial tachycardia may occur in patients without structural heart diseases or taking any medication.
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Comparative Study
Measuring cardiac output in critically Ill patients: disagreement between thermodilution-, calculated-, expired gas-, and oxygen consumption-based methods.
Calculated values of oxygen consumption have been used to calculate a Fick cardiac output when thermodilution measurements are unreliable and when oxygen consumption measurements are unavailable. To determine the accuracy of these calculations, we measured cardiac output in 20 patients by four methods: (1) a reference Fick cardiac output calculated from metabolic oxygen consumption measurements and arterial-venous oxygen content difference (COmet); (2) thermodilution cardiac output (COtherm), (3) an estimated Fick cardiac output based on calculated oxygen consumption using standard equations (COcalc), and (4) an estimated Fick cardiac output using a bedside measurement of expired carbon dioxide production (COexp). ⋯ The mean difference between COexp and COmet was 0.31 +/- 3.01 liters/min. On the basis of these wide confidence intervals, we conclude that (1) thermodilution and metabolic measurements of cardiac output frequently differ in critically ill patients, and (2) estimates of oxygen consumption, based on either standard equations or on expired carbon dioxide production measurements, are poor substitutes for metabolic measurements of oxygen consumption in critically ill subjects and may provide inaccurate estimates of cardiac output.