Continuous ECGs Research Articles

Heart rate variability depression in patients with unstable angina

The degree of reduction in heart rate variability (HRV) after myocardial infarction has been shown to have prognostic significance, but HRV has not been studied extensively in patients with unstable angina. We assessed spectral and nonspectral measurements of HRV in 52 patients with unstable angina, 52 patients with acute myocardial infarction, and 41 normal subjects. The spectral bands of 0.04 to 0.15 Hz (low frequency), 0.15 to 0.4 (high frequency), and nonspectral parameters SDNN, SDANN, SDNN index, rMSSD, and pNN50 were calculated from continuous 24-hour ECGs. All measures of HRV were reduced in patients with acute coronary syndromes compared to normal controls ( p < 0.001), and there was no significant difference in measure of HRV between unstable angina and myocardial infarction patients. In patients with unstable angina who stabilized after admission, HRV had increased by the second 24 hours of monitoring. In contrast, HRV was further depressed in patients who had episodes of chest pain or transient ST-segment depression during the second 24 hours. rMSSD, pNN50, and SDNN index were lower in patients with unstable angina who had transient silent ischemia compared to those without silent ischemia. Of the patients with unstable angina, 4 died and 1 had nonfatal acute myocardial infarction within 11 months. HRV was lower in these patients than in patients without further cardiac events.

ECG interpretation for obstetric nurses

Obstetric nurses are not routinely called on to perform continuous cardiac monitoring or ECGs. However, obstetric nurses will be caring for most pregnant women with cardiac complications. Basic and advanced ECG courses and Advanced Cardiac Life Support (ACLS) courses are offered at most hospitals. Obstetric nurses are encouraged to take advantage of these courses, as even nurses in Level I institutions are caring for patients on continuous ECG monitors. A basic understanding of the ECG is expected of all nurses. Obstetric nurses are encouraged to participate in an ACLS program. Full reviews of the anatomy, physiology, and electrical pathways are available in numerous texts.

Are ioxaglate and iopamidol equally safe and well tolerated in cardiac angiography? A randomized, double-blind clinical study

A randomized, double-blind, parallel-group study was performed in 50 patients undergoing left ventriculography and coronary arteriography to evaluate ECG changes and the effects on left ventricular function of a low-osmolar lonic contrast agent, ioxaglate, as compared with a low-osmolar nonionic contrast medium, iopamidol. Twenty-five patients received ioxaglate (group 1) and 25 patients received iopamidol (group 2). All patients underwent 48 hours of continuous ECG recording beginning 24 hours before the cardiac catheterization. Left ventricular systolic and end-diastolic pressure, peak positive dp dt , and dp/dt/P ratio were measured immediately before and after left ventriculography and 3 minutes later. Left ventricular systolic pressure did not change after injection of either contrast medium. Left ventricular and-diastolic pressure increased by 30% in group 1 ( p < 0.01) and by 22% in group 2 ( p < 0.01) immediately after left ventriculography. A further increase by 45% in group 1 ( p < 0.01) and by 24% in group 2 ( p < 0.01) was observed 3 minutes later. No differences were observed between values obtained in the two groups. Peak positive dp dt did not change immediately after injection of either contrast medium but decreased by 5% (not significant) in group 1 and by 7% ( p < 0.02) in group 2 three minutes after left ventriculography. There were no significant differences between the two groups. Analysis of continuous 48-hour ECGs showed that both ioxaglate and iopamidol induced a slight increase (by 8% and 7%, respectively; p < 0.05) in heart rate during injection with early and complete recovery. A significant increase in the frequency of ventricular premature complexes (total number/1000/hr) was observed in group 2 during the injection period and during the first hour after completion of contrast injection with respect to the extreme intervals ( p < 0.05). Furthermore, bigeminal rhythm, pairs, and R-on-T ventricular premature complexes increased by 24% in group 1 and by 636% in group 2 ( p < 0.02) during injection. PR interval, QRS width, corrected QT interval and ST segment did not change throughout the study. Thus results of our study show that despite simillar effects of ioxaglate and iopamidol on left ventricular function, the occurrence of potentially harmful ventricular arrhythmias is more frequent with iopamidol.

Twelve-lead electrocardiogram recording during percutaneous transluminal coronary angioplasty: Analysis of reciprocal changes

Coronary angioplasty was used as a human model of transient myocardial ischemia to evaluate the electrocardiographic characteristics and significance of “reciprocal” ST-segment depression and T wave changes. Continuous 12-lead ECGs were recorded before and during coronary angioplasty in 20 patients, 19 of whom had single vessel disease. In 12 of 14 patients, LAD occlusion produced ischemic changes (peaked T and/or ST elevation) in L 1, AVL and at least two precordial leads. “Reciprocal” changes (ST depression and/or T inversion) were observed in at least two inferior wall leads. One patient had ST depression in V 4-V 6 with no change in the inferior leads and in the other the only ECG change was inferior ST depression with partial inversion of the T wave. In four of six patients, RCA occlusion produced ischemic changes in at least two inferior wall leads and “reciprocal” changes in L 1, AVL and at least two anterior wall leads. In LAD as well as RCA occlusions “reciprocal” changes were characterized by inversion of the T wave or inversion of its ascending limb with or without ST depression. The magnitude of the ischemic changes tended to be proportional to the magnitude of the “reciprocal” changes. Our data suggest that: (1) “Reciprocal” changes are not a specific indicator of distant myocardial ischemia due to multivessel disease; (2) The magnitude of ischemic changes correlates with the magnitude of “reciprocal” changes; (3) “Reciprocal” changes may be the only manifestation of acute myocardial ischemia; and (4) “Reciprocal” changes may be represented by inversion of the T wave without displacement of the ST-segment.

Comparison of QRS morphologies of spontaneous premature ventricular complexes and ventricular tachycardia induced by programmed stimulation

We addressed the hypothesis that premature ventricular complexes (PVCs) and sustained ventricular tachycardia (VT) have identical QRS morphologies in 20 patients with recurrent sustained VT. Continuous six-lead ECGs of PVCs and sustained VT induced with programmed stimulation were recorded. A computer program divided the PVCs and VT beats of each patient into distinct morphologic groups and a representative waveform was obtained by averaging the PVC and VT beats of the group members. A correlation coefficient was then derived between the QRS complexes of each PVC and VT morphology. The mean number of PVC morphologies was 12 +/- 8 per patient (range 1 to 26), the mean number of VT morphologies was 2 +/- 1 per patient (range 1 to 5). The correlation coefficient between the dominant PVC morphology and a VT morphology was greater than 0.7 in only three patients. The combined percent contribution of all PVCs with morphologies that were at least possibly identical to those of VT averaged only 13%. Thus PVCs with morphologies identical to those of VT are present in some patients with sustained VT, but these constitute a small proportion of all PVCs.

Mexiletine in refractory ventricular arrhythmias.

The antiarrhythmic efficacy of mexiletine was evaluated in 28 subjects with recurrent ventricular tachycardia or fibrillation (22 subjects) or with symptomatic complex ventricular ectopy (six subjects). In all, either the arrhythmia was refractory to other drugs, or such therapy was not tolerated. Response to mexiletine was assessed by continuous ECGs, and in five cases by programmed electrical stimulation. Mexiletine abolished the arrhythmia in 12 cases, but was not tolerated long-term in four. Mexiletine was ineffective in 10 subjects. Seven subjects had significant adverse reactions during short-term dosing; in six, mexiletine was discontinued because of adverse effects after the first few doses so efficacy was not evaluated. The most common adverse effects were nausea, tremor, and generalized malaise. We conclude that mexiletine is an effective antiarrhythmic in some patients with life-threatening ventricular arrhythmias refractory to conventional drugs. Adverse effects significantly limit its use.

ANGINA PECTORIS AND ARRHYTHMIAS DOCUMENTED BY CARDIAC TELEMETRY.

In a dynamic electrocardiographic system which allows the physician to obtain continuous electrocardiograms over a tenhour period in ambulatory subjects, ECG waveforms can be quickly analyzed using rapid-playback oscilloscopes. Diagnostic portions of the recordings can be printed on standard ECG equipment. Several cases demonstrate the numerous applications of recording continuous ECGs in detecting angina pectoris or paroxysmal arrhythmias that cannot be documented using convential electrocardiography.