Pacing and clinical electrophysiology : PACE
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Pacing Clin Electrophysiol · Nov 1990
Effects of increasing heart rate induced by efferent sympathetic neuronal stimulation, isoproterenol or cardiac pacing on myocardial function and oxygen utilization.
The effects of increasing heart rate by six different methods on cardiac function were investigated in 17 open-chest anesthetized dogs. Heart rate was increased approximately 30% by (1) right interganglionic nerve stimulation, (2) atrial pacing, (3) ventricular pacing, (4) atrioventricular sequential pacing, (5) right stellate ganglion stimulation, and (6) isoproterenol administration. During heart rate increases induced by atrial pacing left ventricular intramyocardial pressure, coronary blood flow, oxygen delivery per unit of myocardial oxygen consumption, and myocardial efficiency were unchanged. ⋯ Increases in heart rate induced by right interganglionic nerve stimulation did not alter myocardial oxygen consumption, or the index of cardiac efficiency. It is concluded that augmentation of heart rate by either ventricular or atrioventricular pacing impairs myocardial function so that there is a decrease of left ventricular efficiency and isoproterenol augments chronotropism and myocardial force relative to cardiac external work so there is a reduction in cardiac efficiency. In contrast, atrial pacing or right interganglionic nerve stimulation augments chronotropism such that myocardial oxygen consumption and efficiency are unchanged.
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Pacing Clin Electrophysiol · Sep 1990
Comparative StudyA prospective study of right ventricular pulse pressure and dP/dt to discriminant-induced ventricular tachycardia from supraventricular and sinus tachycardia in man.
In the future, automatic implantable cardioverter defibrillators (AICD) may incorporate sensors to differentiate hemodynamically stable from unstable ventricular tachycardias (VT). These sensors should also discriminate between ventricular and supraventricular tachycardias to avoid inappropriate responses from the device. Right ventricular pulse pressure (RVPP) and maximal systolic right ventricular dP/dt (dP/dt) were measured before, during and after 91 episodes of hemodynamically stable VT (VTs), hemodynamically unstable VT (VTus), supraventricular tachycardia (SVT) and sinus tachycardia (ST) induced in 49 male patients. ⋯ Percent change RVPP separated each episode of VTs and VTus from those of ST. The range of common values for % delta dP/dt between all four groups was extensive. It is concluded that % delta RVPP from baseline is significantly different between groups of patients during VTs, VTus, SVT, and ST, but that a large degree of overlap in the range of values for % delta RVPP and RV dP/dt between different arrhythmias groups may limit the specificity of these hemodynamic variables in separating different arrhythmias.
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Pacing Clin Electrophysiol · Aug 1990
Case ReportsReversible myocardial depression in survivors of cardiac arrest.
Three patients under 40-years old who survived cardiac arrest due to ventricular fibrillation were originally diagnosed as having idiopathic dilated cardiomyopathy. Shortly after cardiac arrest, assessment of myocardial function revealed a globally dilated left ventricle in each patient with an estimated ejection fraction between 20% and 30%. ⋯ These findings suggest that myocardial stunning due to hypoperfusion during ventricular fibrillation or the effects of transthoracic shocks may result in profound, reversible myocardial depression in survivors of cardiac arrest. Serial evaluation of left ventricular function may be of value in selected survivors of cardiac arrest in order to evaluate time-dependent resolution of myocardial dysfunction and may prevent misdiagnosis of idiopathic dilated cardiomyopathy.
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Pacing Clin Electrophysiol · Jul 1990
Comparative StudyAtrial and ventricular stimulation threshold development: a comparative study in patients with a DDD pacemaker and two identical carbon-tip leads.
The atrial and ventricular pacing threshold development during the first postoperative year was studied in a group of patients receiving DDD pacemakers. Identical carbon-tip endocardial leads were implanted in atrium and ventricle. Atrial and ventricular voltage stimulation thresholds were measured at implantation, and noninvasively at 1 and 12 months thereafter. ⋯ The ratio of chronic to acute stimulation thresholds was higher on the ventricular than on the atrial level (0.001 greater than P greater than 0.0005). The chronic atrial threshold showed a logarithmic relation to the threshold at implantation (P = 0.0006); postoperative threshold rise was not a significant determinant of the chronic atrial threshold (P = NS). On the ventricular level, the reverse was seen: The chronic threshold was related to the postoperative threshold rise (P = 0.0015, logarithmic relation), but not to the implantation threshold (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
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Pacing Clin Electrophysiol · Jun 1990
A study of the use of flecainide acetate in the long-term management of cardiac arrhythmias.
One hundred and sixty-nine patients with a wide range of cardiac arrhythmias and who had been treated with chronic oral flecainide acetate were reviewed retrospectively. The most common arrhythmia was atrial fibrillation (32%), and 20% of the patient population had the Wolff-Parkinson-White syndrome. Five hundred and three treatment episodes were assessed, 254 with flecainide alone or in combination, mean duration 7.3 +/- 9.4 months, and 249 without flecainide, mean duration 9.5 +/- 12.3 months. ⋯ Arrhythmia frequency was reduced or abolished in 73% of flecainide treatment episodes, with little difference between arrhythmia groups. Unwanted effects were seen in 14% of flecainide treatment episodes, and half of these cases were managed by dose adjustment. It is concluded that flecainide acetate is effective in a wide range of cardiac arrhythmias, and that long-term management problems are few.