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ABSTRACT: ECGs from thorough QT studies must be read in a central laboratory by trained experts. Standards of expertise are not presently defined. We, therefore, studied the use of Z-scores to define reader competence.
Two hundred ECGs were read by 24 experts and the mean and standard deviation (SD) of QT measurements calculated for each ECG. Z-scores ([QT(reader)- mean QT(experts)]/ SD(experts)) for each ECG and mean of absolute Z-scores of all ECGs read by a reader were calculated. The highest mean absolute Z-score of experts was considered the cutoff to define competence. Hundred of these standardized ECGs were used to assess performance of readers from the central laboratory.
All experts had mean absolute Z-scores < or = 1.5. Using this cutoff, one of 28 experienced readers and 7 of 15 trainees had unacceptable Z-scores. After re-training, all achieved Z-scores <1.5. Comparing histograms of actual Z-scores of the 100 ECGs of readers with unacceptable scores with that of the reader with the best Z-score showed two patterns. Readers with histograms having a peak and tails similar to that of the best reader, but with leftward or rightward shift, consistently made shorter or longer QT measurements, respectively. A histogram with a flatter peak and wider tails, suggested that measurements were long in some ECGs and short in others.
Mean absolute Z-score is useful to assess competence for measuring the QT interval on ECGs. Analysis of histograms can pinpoint problems in QT measurements.
Annals of Noninvasive Electrocardiology 01/2009; 14(1):19-25. · 1.10 Impact Factor
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ABSTRACT: Idiopathic ventricular tachycardia is a defined set of tachycardias when structural or pathological cause has been ruled out for the same. This paper tries to define and classify these arrhythmias to organize a logical therapeutic approach to deal with them. 60-80% of the idiopathic tachycardias originate from the right ventricular outflow tract (RVOT) and in 10% from the left ventricular outflow tract (LVOT). Outflow tract tachycardias have either LBBB or RBBB morphology with early R wave transition in chest leads. Adenosine, beta blockers and calcium channel blockers is the common medical treatment. Radiofrequency ablation is however the treatment of choice. Verapamil sensitive left ventricular tachycardia (ILVT) and propranolol sensitive left ventricular tachycardia (IPVT) are the other two forms recognized. RF ablation seems ideal for long-term management of ILVT and implantable cardioverter defibrillator (ICD) for IPVT. Inherited channelopathies include catecholaminergic polymorphic ventricular tachycardia (CPVT), Brugada syndrome and long QT syndrome where there is an inherited disorder in the ion-exchange channels of the cell-membrane leading to tachycardia. Prognosis in these is variable; CPVT, in particular, has a malignant course when untreated. RF ablation and placement of an ICD are important in the overall management of specific arrhythmia.
The Journal of the Association of Physicians of India 05/2007; 55 Suppl:33-8.
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ABSTRACT: Cardiomyopathy due to various ventricular and supraventricular arrhythmias, including isolated cases of atypical atrioventricular nodal reentrant tachycardia, have been described. In this case report typical slowfast atrioventricular nodal reentrant tachycardia resulting in cardiomyopathy is being documented for the first time. In the setting of depressed left ventricular function, an episode of tachycardia pushed this patient into heart failure. Radiofrequency ablation of the slow pathway was successful in eliminating her tachycardia with the return of left ventricular function to normal. A follow-up of two years post-ablation revealed the patient to be symptom-free.
Indian heart journal 57(6):723-4.
