Biventricular pacing attenuates T-wave alternans and T-wave amplitude compared to other pacing modes.

BACKGROUND: The impact of altered ventricular activation, including biventricular (BV) pacing, on T-wave alternans (TWA) and arrhythmic substrates is unclear. We studied how differing ventricular activation sequence alters TWA; the interval from peak-to-end of the T-wave (TpTe) and T-wave amplitude during right (RV), left (LV), and biventricular (BV) pacing; and right atrial (RA) pacing in patients with preexisting conduction delay. METHODS AND RESULTS: We measured TWA during RA, RV, LV, and BV pacing in 33 patients receiving cardiac-resynchronization-therapy-defibrillators. TWA magnitude (V(alt)) was lower during BV than RV (P < 0.01), RA (P < 0.01), or LV pacing. As a result, BV-TWA was more often negative than RV-TWA (P < 0.01), LV-TWA, and RA-TWA, particularly when discordant between pacing modes (P < 0.01). Overall, 83% of TWA recordings were abnormal (25% indeterminate), and 17% negative. BV pacing reduced T-wave amplitude (P < 0.05) and TpTe (P < 0.005) compared to RV pacing and LV pacing (P < 0.05; P < 0.005 respectively). Notably, TWA magnitude varied linearly with T-wave amplitude for all pacing modes (P < 0.001). Over 410 +/- 252 days' follow-up, RV-TWA predicted the combined endpoint of death and ICD therapy with 86% negative predictive value (P < 0.05). BV-TWA, RA-TWA, and other repolarization indices were not predictive. CONCLUSIONS: BV pacing attenuates TWA in tandem with reduced T-wave magnitude. In these patients with baseline QRS prolongation, RV-TWA predicted events more effectively than BV-TWA and RA-TWA. Further studies are required to understand how altered ventricular activation influences repolarization dynamics and arrhythmic tendency.

Accuracy of electrocardiogram interpretation by cardiologists in the setting of incorrect computer analysis.

BACKGROUND: Overreading of 12 lead electrocardiograms (ECGs) is required to circumvent errors of computerized ECG interpretation. The accuracy of the overreading physician's interpretation of ECGs that were incorrectly read as atrial fibrillation by a computer algorithm has not been systematically examined. METHODS: A total of 2298 ECGs with the computerized interpretation of atrial fibrillation from 1085 patients were analyzed by 2 electrophysiologists, who identified 442 ECGs (19%) from 382 patients (35%) that were incorrectly interpreted as atrial fibrillation. Charts were reviewed to determine the interpretation of the ECG by the ordering physician (primary reader) and the overreading cardiologist. RESULTS: Cardiologists as primary readers more often corrected the misinterpreted ECGs as compared with internists, emergency physicians, or other specialists (94% vs 71%, P < .001). Surprisingly, interpretations by cardiologists as primary readers were more accurate than the interpretation provided by overreading cardiologists (94% vs 72%, P < .001). CONCLUSION: Knowledge of an individual patient on whom an ECG is ordered may result in a more critical rhythm assessment and might account for the higher accuracy of rhythm interpretation by the cardiologist as compared with the interpretation by the overreading cardiologist who is lacking relevant clinical information.

Beta blockers as anti-arrhythmic agents.

Although beta-adrenergic blocking agents are not always considered anti-arrhythmic drugs, the results of several recent trials have suggested an anti-arrhythmic mechanism for at least part of their mortality benefit in the treatment of chronic congestive heart failure. We review background experimental and clinical evidence for the anti-arrhythmic actions of beta-blockers and then review the results of published beta-blocker heart failure trials. A majority of trials showed improvement in overall survival as well as reduction in sudden death and ventricular arrhythmias with beta-blocker treatment. Although different effects were seen with different specific agents, these trials overall support a clinically significant anti-arrhythmic effect of several beta-blockers.

Misdiagnosis of atrial fibrillation and its clinical consequences.

PURPOSE: Computer algorithms are often used for cardiac rhythm interpretation and are subsequently corrected by an overreading physician. The purpose of this study was to assess the incidence and clinical consequences of misdiagnosis of atrial fibrillation based on a 12-lead electrocardiogram (ECG). METHODS: We retrieved 2298 ECGs with the computerized interpretation of atrial fibrillation from 1085 patients. The ECGs were reinterpreted to determine the accuracy of the interpretation. In patients in whom the interpretation was incorrect, we reviewed the medical records to assess the clinical consequences resulting from misdiagnosis. RESULTS: We found that 442 ECGs (19%) from 382 (35%) of the 1085 patients had been incorrectly interpreted as atrial fibrillation by the computer algorithm. In 92 patients (24%), the physician ordering the ECG had failed to correct the inaccurate interpretation, resulting in change in management and initiation of inappropriate treatment, including antiarrhythmic medications and anticoagulation in 39 patients (10%), as well as unnecessary additional diagnostic testing in 90 patients (24%). A final diagnosis of paroxysmal atrial fibrillation based on the initial incorrect interpretation of the ECGs was generated in 43 patients (11%). CONCLUSION: Incorrect computerized interpretation of atrial fibrillation, combined with the failure of the ordering physician to correct the erroneous interpretation, can result in the initiation of unnecessary, potentially harmful medical treatment as well as inappropriate use of medical resources. Greater efforts should be directed toward educating physicians about the electrocardiographic appearance of atrial dysrhythmias and in the recognition of confounding artifacts.