Paul F. Walter

Influence of left ventricular function on signal averaged late potentials in patients with coronary artery disease with and without ventricular tachycardia

Left ventricular dysfunction has been suggested as a cause of late potentials on the signal averaged ECG of patients with coronary artery disease. We compared the averaged surface ECG with angiographic findings in 57 patients with coronary artery disease and left ventricular dysfunction. Sixteen patients had sustained ventricular tachycardia and 41 had no documented arrhythmia. These two patient groups were comparable with respect to age, mean ejection fraction, and wall motion score. Late potentials, defined as voltage less than 25 microV in the last 40 msec of the filtered QRS complex, were found in 10 of 16 patients with ventricular tachycardia and in 6 of 41 patients without arrhythmia (p less than 0.005). However, late potentials were independent of ejection fraction, wall motion score, or presence of dyskinesis in both groups. There was no correlation between the total filtered QRS duration and ejection fraction or wall motion score in either patient group. In patients with coronary artery disease, late potentials are associated with ventricular tachycardia but are independent of global or regional left ventricular function. This finding has important implications for studies of the prognostic value of late potentials following myocardial infarction.

Transcutaneous Doppler method of measuring cardiac output--II. Noninvasive measurement by transcutaneous Doppler aortic blood velocity integration and M mode echocardiography.

In 15 patients with acute myocardial infarction (group I) and in 14 patients undergoing routine cardiac catheterization (group II) cardiac output values obtained by multiplying the 1 minute sum of the systolic integral of aortic blood flow velocity by the average systolic diameter of the aortic root were compared with values obtained with the thermodilution and Fick methods, respetively. Patients in group I were studied under various hemodynamic conditions, whereas those in group II were studied in the baseline state conditions, whereas those in group II were studied in the baseline state only. In group I, the correlation between the two methods was excellent (r values ranged from 0.96 to 0.99) except in one severely anemic patient whose Doppler signals were noisy, but at heart rates exceeding 150 beats/min it was not as good. In group II, the correlatin between the two methods was r = 0.96 with a standard error of the estimate of 0.226 liter. The Doppler method is totally noninvasive and is useful for monitoring changes in cardiac output in patients with acute myocardial infarction.

Anatomy of atrioventricular nodal reentry investigated by intracardiac echocardiography.

Intracardiac echocardiography was used to evaluate posteroseptal space anatomy in patients with atrioventricular nodal reentrant tachycardia compared with patients with other mechanisms of tachycardia. The posteroseptal space was found to be significantly wider in patients with atrioventricular nodal reentry, suggesting an anatomic basis for dual atrioventricular nodal physiology.

Transcutaneous method of measuring Doppler cardiac output—I: Comparison of transcutaneous and juxta-aortic Doppler velocity signals with catheter and cuff electromagnetic flowmeter measurements in closed and open chest dogs☆

Cardiac output values obtained by thermodilution technique in 20 closed and open chest dogs were compared with values obtained by multiplying the integral of Doppler systolic velocity signals of aortic flow in 1 minute by the cross-sectional area of the aortic root. Doppler velocity signals were measured either from immediately outside the proximal aortic wall or from outside the chest wall during (1) the baseline state, (2) after 500 ml of hemorrhage, and (3) after reinfusion, (4) after administration of propranolol, and (5) during infusion of dopamine. In addition, Doppler stroke volume waveforms were compared with those obtained by electromagnetic flowmeter. Results showed a close similarity between Doppler signals and electromagnetic waveforms, and a close correlatin between Doppler and thermodilution values for cardiac output except at heart rates exceeding 160 beats/min. The studies showed the transcutaneous Doppler method of measuring cardiac output to be an accurate and reliable technique with application to clinical heart disease.

Tilt table testing with video EEG monitoring in the evaluation of patients with unexplained loss of consciousness.

It is well established that convulsive movements often accompany syncopal events yet many patients with these clinical features are misdiagnosed with seizures and often referred to epilepsy centers because they are refractory to treatment with anticonvulsant medications. Tilt table testing is the gold standard for diagnosing vasodepressor syncope, but it can fail to provide clinical details that help distinguish convulsive syncope from epileptic seizures and psychogenic events. This study evaluates the diagnostic utility of the addition of video and EEG monitoring during tilt table testing for patients with refractory episodes of unexplained loss of consciousness. Retrospective analysis was performed of 40 consecutive patients who were referred to the Emory Epilepsy Center and underwent tilt table testing with concomitant video-EEG between March 1, 2007 and December 1, 2008. EEG was recorded throughout the study in addition to video recording and single channel EKG. Events were classified as vasodepressor syncope, pre-syncope, or psychogenic. Tilt combined with video EEG was diagnostic in 26/40 (65%) of patients. Vasodepressor syncope was seen in 17/40 (42.5%), 9 of which had associated involuntary movements. Three patients experienced psychogenic non-epileptic events. Antiepileptic drugs (AEDs) were being prescribed for 17 patients, 7 of which were discontinued as a result of the testing. The majority of patients (38/40) had undergone prior neurological and cardiac evaluation with routine EEG, neuroimaging and/or Holter monitoring. Patients with convulsive syncope are often misdiagnosed and treated with AEDs despite prior neurodiagnostic and cardiac evaluation. Tilt table testing with video-EEG is useful in patients with refractory episodes of unexplained loss of consciousness and can avoid expensive non-diagnostic evaluations as well as ongoing treatment with unnecessary AEDs.

Right Ventricular Outflow Tract Tachycardia as a Result of Blunt Chest Trauma

Two patients presented with monomorphic ventricular tachycardia after blunt chest trauma. In both cases, the arrhythmia had a left bundle branch block, inferior axis morphology comparable to that seen with idiopathic ventricular tachycardia originating from the right ventricular outflow tract (RVOT). In one patient, the arrhythmia persisted and required catheter ablation. A history of cardiac trauma should be considered in patients presenting with RVOT tachycardia.

Rapid Ventricular Tachycardia Due to His‐Purkinje Reentry

Two patients developed rapid His‐Purkinje reentrant tachycardia during programmed ventricular stimulation for evaluation of recurrent ventricular tachycardia. In Patient 1, His‐Purkinje reentry induced a morphologically distinct ventricular tachycardia which may have been a reentrant circuit operating independently for several cardiac cycles. His‐Purkinje reentry was not inducible in Patient 2 until lidocaine was given. Following lidocaine administration, sustained His‐Purkinje reentrant tachycardia was initiated by 2 premature ventricular stimuli. The tachycardia was rapid (240 beats per minute) and required cardio‐version.

Angiographic demonstration of inhibition of methyl-ergonovine-induced coronary vasospasm in a patient with sudden death

A case is presented illustrating the association of spontaneous coronary vasospasm with sudden death. Serial angiography and challenge with methyl-ergonovine were performed to document the effectiveness of medial therapy. The use and safety of ergonovine testing in patients with spasm-related sudden death are reviewed.

Response to Letter Regarding Article, “Hands-On Defibrillation: An Analysis of Electrical Current Flow Through Rescuers in Direct Contact With Patients During Biphasic External Defibrillation”

We are grateful for J.L. Sullivan’s interest in and comments regarding our article.1 Clearly, the use of polyethylene gloves is an important constraint to our experiments (We mention this in the article more than once). However, such gloves are a part of standard precautions during resuscitation. Moreover, we clearly demonstrate the safety of hands-on defibrillation in humans despite a direct bare-skin–to–bare-skin return current pathway between the patient and rescuer.nnShould …