Hemodynamic evaluation of common cardiac arrhythmias

Hemodynamic effects of arrhythmias are considered to be relatively unimportant unless the heart rate is very slow or very rapid. The present study describes a simple method which enables determination of beat-to-beat changes in stroke volume, cardiac output, double product and cardiac efficiency expressed as the interrelationship between the last two parameters. It is obtained by calculating stroke volume from directly measured values of arterial pressure, using a modification of a formula described for irregular rhythms. The calculated parameters are expressed as the percentage of the values of the sinus beat or state occurring with normal cardiac rhythm. The results confirmed that atrial ectopic beats have a less deleterious effect on myocardial function than those from ventricular or nodal origin. The change in stroke volume or cardiac output may be accompanied by either a decreased or increased double product and/or cardiac efficiency. This depends on the type of arrhythmia, the number of ectopic beats per minute and the condition of the patient's heart. The method provides measurement of this parameter in a given patient at a given state as well as at other different frequencies of the same arrhythmia. It demonstrates then which frequency induces hemodynamic changes of sufficient degree to justify antiarrhythmic therapy. The method may be useful in optimising care of patients in units for critical care, or even in outpatient departments.