Selected Abstracts > Arrhythmia

Title: A quantitative assessment of T-wave morphology in LQT1, LQT2, and healthy individuals based on Holter recording technology

(Heart Rhythm Jan 2008;5:11-18)

BACKGROUND; The clinical course and the precipitating risk factors in the congenital long QT syndrome (LQTS) are genotype specific.

OBJECTIVES: The goal of this study was to develop a computer algorithm allowing for electrocardiogram (ECG)-based identification and differentiation of LQT1 and LQT2 carriers.

METHODS: Twelve-lead ECG Holter monitor recordings were acquired in 49 LQT1 carriers, 25 LQT2 carriers, and 38 healthy subjects as controls. The cardiac beats were clustered based on heart-rate bin method. Scalar and vectorial repolarization parameters were compared for similar heart rates among study groups. The Q to Tpeak (QTpeak), the Tpeak to Tend interval, T-wave magnitude and T-loop morphology were automatically quantified using custom-made algorithms.

RESULTS: QTpeak from lead II and the right slope of the T-wave were the most discriminant parameters for differentiating the 3 groups using prespecified heart rate bin (75.0 to 77.5 beats/min).The predictive model utilizing these scalar parameters was validated using the entire spectrum of heart rates. Both scalar and vectorcardiographic models provided very effective identification of tested subjects in heart rates between 60 and 100 beats/min, whereas they had limited performance during tachycardia and slightly better discrimination in bradycardia. In the 60 to 100 beats/min heart rate range, the best 2-variable model identified correctly 89% of healthy subjects, 84% of LQT1 carriers, and 92% of LQT2 carriers. A model including 3 parameters based purely on scalar ECG parameters could correctly identify 90% of the population (89% of healthy subjects, 90% of LQT1 carriers, and 92% of LQT2 carriers).

CONCLUSION: Automatic algorithm quantifying T-wave morphology discriminates LQT1 and LQT2 carriers and healthy subjects with high accuracy. Such computerized  ECG methodology  could assist physicians evaluating subjects suspected for LQTS.

Title: New algorithm using only lead aVR for differential diagnosis of wide QRS complex tachycardia

(Heart Rhythm jan 2008;5:89 -98)

BACKGROUND: We recently reported an ECG algorithm for differential diagnosis of regular wide QRS complex tachycardias that was superior to the Brugada algorithm.

OBJECTIVE: The purpose of this study was to further simplify the algorithm by omitting the complicated morphologic criteria and restricting the analysis to lead aVR.

METHODS: In this study, 483 wide QRS complex tachycardias [351 ventricular tachycardias (VTs), 112 supraventricular tachycardias (SVTs), 20 preexcited tachycardias] from 313 patients with proven diagnoses were prospectively analyzed by two of the authors blinded to the diagnosis. Lead aVR was analyzed for (1) presence of an initial R wave, (2) width of an initial r or q wave
40 ms, (3) notching on the initial downstroke of a predominantly negative QRS complex, and (4) ventricular activation-velocity ratio (vi/vt),the vertical excursion (in millivolts) recorded during the initial (vi) and terminal (vt) 40 ms of the QRS complex. When any of criteria 1 to 3 was present, VT was diagnosed; when absent, the next criterion was analyzed. In step 4, vi/vt
1 suggested SVT, and vi/vt
1 suggested VT.

RESULTS: The accuracy of the new aVR algorithm and our previous algorithm was superior to that of the Brugada algorithm (P .002 and P .007, respectively). The aVR algorithm and our previous algorithm had greater sensitivity (P .001 and P .001, respectively) and negative predictive value for diagnosing VT and greater specificity (P .001 and P .001, respectively) and positive predictive value for diagnosing SVT compared with the Brugada criteria.

CONCLUSION :The simplified aVR algorithm classified wide QRS complex tachycardias with the same accuracy as standard criteria and our previous algorithm and was superior to the Brugada algorithm.

Title: Electrocardiographic factors playing a role in ischemic ventricular fibrillation in ST elevation myocardial infarction are related to the culprit artery

(Heart Rhythm 2008;5:71-78) © 2008 Heart Rhythm Society

BACKGROUND:
Sudden cardiac death caused by ischemic ventricular fibrillation (VF) associated with ST elevation myocardial infarction (STEMI) is one of the most frequent causes of death.

OBJECTIVE:

 We hypothesized that electrocardiographic (ECG) characteristics differ between STEMI patients with and without ischemic VF.

METHODS :
Fifty-five first STEMI patients with at least one 12-lead ECG recorded before ischemic VF were compared with 110 first STEMI patients without ischemic VF. Patients with bundle
branch blocks or high-degree atrioventricular blocks with escape rhythms were not included. ECG measurements were performed manually after scanning the ECG with the most prominent ST deviation into a software environment and magnifying it 4 times.

RESULTS :
Mean age was 57
12 years, and 126 patients were male. No differences were present between the VF and control group regarding baseline, enzymatic, and angiographic data. In
left circumflex artery and right coronary artery myocardial infarction,a longer QRS interval (109
23 ms vs. 91
16 ms, P  .02 and 107
24 ms vs. 93
19, P  .02) was present. In the latter the PR interval (211
64 ms vs. 160
36 ms, P .001) and ST deviation score (3.6
1.0 mV vs. 1.7
1.5 mV, P .001) were also increased. In the left anterior descending artery group no differences in conduction intervals and ST deviation score were present.

CONCLUSION :
Longer PR and QRS intervals in right coronary artery and left circumflex artery MI fit with the perfusion and activation pattern of the atrioventricular node and the ventricular myocardium. Myocardium perfused by the left anterior descending artery is activated earliest, hiding any intraventricular conduction delay within the QRS complex. Intramural slowed conduction could
be a substrate for ischemic VF.