The American journal of cardiology
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Randomized Controlled Trial Clinical Trial
Evaluation by exercise Doppler echocardiography of maintenance of cardiac output during ventricular pacing with or without chronotropic response.
To examine the effectiveness of activity-initiated rate-responsive pacing, this study assessed the increases in stroke volume and cardiac output during randomized treadmill exercise in rate-responsive and fixed-rate ventricular (VVI) pacing in 10 patients. Stroke volume index and cardiac index were determined by suprasternal Doppler measurements. ⋯ These findings indicate that VVI pacing increased stroke volume more than did rate-responsive pacing, especially in younger patients, but the increase in cardiac output was less than that seen with rate-responsive pacing due to the absence of chronotropic response. Accordingly, an activity-sensing, rate-responsive pacemaker can effectively increase the heart rate, significantly augment cardiac output and extend the duration of exercise.
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Randomized Controlled Trial Multicenter Study Comparative Study Clinical Trial
Esmolol versus verapamil in the acute treatment of atrial fibrillation or atrial flutter.
The effects of esmolol, an ultrashort-acting beta blocker, and verapamil were compared in controlling ventricular response in 45 patients with atrial fibrillation or atrial flutter, in a randomized, parallel, open-label study. Patients with either new onset (less than 48 hours, n = 31) or old onset (greater than 48 hours, n = 14) of atrial fibrillation or flutter with rapid ventricular rate were stratified to receive esmolol (n = 21) or verapamil (n = 24). Drug efficacy was measured by ventricular rate reduction and conversion to sinus rhythm. ⋯ Mild hypotension was observed in both treatment groups. Esmolol compares favorably with verapamil with respect to both efficacy and safety in acutely decreasing ventricular response during atrial fibrillation or flutter. Moreover, conversion to sinus rhythm is significantly more likely with esmolol.
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Review of 18 published reports before the widespread use of cardiac care units disclosed that the frequency of rupture of the left ventricular free wall or ventricular septum among necropsy cases of acute myocardial infarction (AMI) ranged from 4 to 24% (mean 8%) (619 of 7,905 cases). The frequency of rupture of the left ventricular free wall or ventricular septum among necropsy patients with fatal AMI studied in this laboratory since 1968 was analyzed. ⋯ Thus, the frequency of rupture of the left ventricular free wall or ventricular septum during AMI appears to have increased substantially since the widespread use of coronary care units. Also, the frequency of rupture is nearly 3 times greater in those in whom rupture occurred during the first AMI compared to those with a previous infarct that healed.