Mouse heart rate in a human: diagnostic mystery of an extreme tachyarrhythmia.

We report telemetry recording of an extreme non-fatal tachyarrhythmia noted in a hospitalized quadriplegic male with history of atrial fibrillation where the average ventricular conduction rate was found to be about 600 beats per minute and was associated with transient syncope. A medical literature review suggests that the fastest human ventricular conduction rate reported to date in a tachyarrhythmia is 480 beats per minute. We therefore report the fastest human heart rate noted in a tachyarrhythmia and the most probable mechanism of this arrhythmia being a rapid atrial fibrillation with 1:1 conduction in the setting of probable co-existing multiple bypass tracts.

Utility of the frontal plane QRS axis in identifying non-ST-elevation myocardial infarction in patients with poor R-wave progression.

Poor R-wave progression (PRWP) is a common electrocardiographic phenomenon in which the anticipated increase in R-wave amplitude in successive precordial leads, V(1) to V(5), fails to occur. PRWP is prevalent in approximately 10% of hospitalized adult patients, predominantly in those with coronary artery disease. Debate is ongoing on its association with myocardial infarction (MI). However, studies that showed no association failed to appraise the significance of the QRS axis in relation to PRWP among such patients with MI. In our retrospective study, we consecutively identified 150 unselected adult patients with PRWP among 660 successive admissions to the general medical floors of a tertiary care teaching hospital (Saint Vincent Hospital, Worcester, Massachusetts). After excluding patients with anterior wall Q-wave MI (defined as the presence of a QS complex or Q-wave > or =1 mm deep in V(2) or V(3)), sudden unexpected death, MI after percutaneous coronary interventions or coronary artery bypass grafting during this hospitalization, Wolff-Parkinson-White syndrome, pacemakers, bundle branch blocks, and electrocardiograms that were of poor quality or affected by severe motion artifact, inconsistencies with patient identification, or errors in lead placement, 137 patients remained. The patients were then screened for non-ST-segment elevation MI (NSTEMI) during the present admission. The DePace criteria for PRWP were systematically used for all patients, and the QRS axis was calculated using limb leads based on Einthoven's equilateral triangle (normal was considered -30 degrees to 100 degrees ). Of the 137 study patients screened with PRWP, 38 had NSTEMI (25.3%). Thirty-one had a normal QRS axis (mean age +/- standard deviation 71.3 +/- 12 years), and 7 showed either right or left axis deviation (mean age +/- standard deviation 64.3 +/- 15 years). This proved to be statistically significant (p <0.0001) within this cohort of NSTEMI patients. In conclusion, PRWP determined using the DePace criteria in the presence of a normal QRS axis appears to be more significantly associated with the presence of overall MI within this cohort of NSTEMI patients.

Induction of atrial depolarization abnormality during dipyridamole stress imaging: a cautionary note.

P-wave widening on the 12-lead electrocardiogram denotes abnormal atrial depolarization and has been shown to be associated with myocardial ischemia during treadmill exercise tolerance testing. However, its true significance during dipyridamole (Persantine) stress imaging remains questionable given the potential direct as well as indirect effects of dipyridamole on the atria. We present a novel series of 5 comparable cases of dipyridamole stress imaging where serial P-wave duration increase occurred during administration of dipyridamole. We observed that such P-wave widening occurred even in the absence of evidence of myocardial ischemia on subsequent myocardial perfusion imaging. Clinicians should therefore be aware of this potential association where, unlike that observed with graded exercise treadmill testing, P-wave widening during dipyridamole infusion could perhaps be a pharmacological effect on the atria instead of an indication of underlying myocardial ischemia.

Quantitative estimation of left atrial linear dimension on a transthoracic echocardiogram using an electrocardiographic formulaic assessment.

A proportionate and incremental association between left atrial (LA) dilatation on a transthoracic echocardiogram (TTE) and increasing severity in abnormal atrial depolarization can be described by the regression formula: LA dimension in parasternal long-axis view (in millimeters) = 2.47 + 0.29 [P-wave duration (in milliseconds)]. However, prospective testing of this formula for LA quantification with comparison to other TTE indexes is lacking. We prospectively obtained 12-lead electrocardiograms for 72 consecutive patients before individual, nonemergent TTE assessment. P waves were assessed independently to the nearest 10 ms for application of the formula with a Bland-Altman plot. P-wave durations were obtained specifically from lead II and also from any lead that yielded the widest measurement. There was a strong formulaic correlation with LA measurement by TTE (p <0.00000001; r = 0.662), irrespective of electrocardiographic lead used. However, as the measurement difference increased between that in any lead and lead II, correlation strength increased. Correlation was not significantly affected by commonly measured electrocardiographic and TTE indexes, such as, PR interval, QRS complex, and left ventricular end-diastolic as well as systolic dimensions, after adjustment for these variables. Moreover, when the P-wave axis remained within the normal range, the correlation strength increased. The Bland-Altman plot also showed good agreement of LA dimension assessment between formulaic estimation and TTE measurement. In conclusion, there is good agreement and correlation between formulaic estimation and that of TTE for measurement of LA linear dimension. The LA regression formula is an indirect asset that could perhaps supplement LA quantification on TTE in certain circumstances.

Association of P-wave duration, dispersion, and terminal force in relation to P-wave axis among outpatients.

BACKGROUND: While P-wave duration (P-dur) and dispersion (P-disp) could both reflect fractionated and inhomogeneous propagation of sinus cardiac impulses, and may therefore be associated with each other, a clear relationship has not been extensively studied. We studied these markers as well as the significance of P-wave terminal force in lead V1 (PTFV1) in relation to the P-wave axis (P-axis). METHODS: We appraised our previously studied sample of 500 consecutively numbered, otherwise unselected, electrocardiograms (ECGs) of outpatients from the University of Massachusetts, Worcester, Massachusetts, for the foregoing P-wave characteristics. P-disp, defined as the difference of the duration between the widest and narrowest P wave, and the greatest P-dur after a 12-lead ECG search, was measured manually to the nearest 10 ms. PTFV1 was considered positive when > or = 40 mm2 terminal deflection was present on biphasic P waves on lead V1. Normal P-axis was considered 0 degrees to +75 degrees by manually constructing the mean frontal plane electrical P-axis from standard limb leads. RESULTS: After excluding those with atrial arrhythmias, paced rhythms, errors in lead placement, P waves with low amplitude or overall technically poor tracing, 428 ECGs formed our final sample. P-dur was strongly associated with P-disp (P < 0.0001), but the correlation remained weak (r = 0.42). Overall, P-dur was not significantly associated with P-axis but when divided into tertiles and quintiles, the significance was evident within the range of the normal P-axis, particularly 0 degrees to +60 degrees (P < 0.0001). In a subanalysis of 380 ECGs that had appreciable biphasic P waves on lead V1, PTFV1 was noted on 178 (47%) ECGs and was significantly associated with P-dur (P < 0.0001), P-disp (P < 0.0001), and P-axis (P = 002). When considering P-axis in tertiles and quintiles, P-dur was greater in patients with a positive PTFV1 and significant within the normal range of the P-axis, especially from 0 degrees to +60 degrees . CONCLUSION: P-dur, P-disp, and PTFV1 appear to share a significant tripartite association in relation to the normal P-axis, particularly when P-axis ranges 0 degrees to +60 degrees . Therefore, for optimal clinical assessment, these markers should be evaluated in relation to the normal P-axis.

Abnormal atrial depolarization associated with Chiari network?

The Chiari network, a congenital remnant of fetal membrane in the right atrium, is infrequently associated with complications, such as supraventricular tachyarrhythmias. There have however been no known reports of basic electrocardiographic significance of the Chiari network. We present three consecutive cases of Chiari network found in the presence of abnormal interatrial conduction (P-waves > or = 110 ms), which is a potential predictor of atrial tachyarrhythmias.