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Heart Rhythm. 2014 Aug;11(8):1361-6. doi: 10.1016/j.hrthm.2014.04.025. Epub 2014 Apr 19.

Use of an electrocardiographic screening tool to determine candidacy for a subcutaneous implantable cardioverter-defibrillator.

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Division of Cardiology, Department of Medicine, Northwestern University, Chicago, Illinois.
Division of Cardiology, Department of Medicine, Northwestern University, Chicago, Illinois. Electronic address:



An electrocardiographic (ECG) screening test has been developed to identify patients being considered for a totally subcutaneous implantable cardioverter-defibrillator (S-ICD) at risk for T-wave oversensing.


The purpose of this study was to determine the proportion of potential S-ICD recipients who fail the ECG screening test and to identify predictors of failure.


Patients who already have an ICD but are not receiving antibradycardia pacing are representative of patients who might be considered for an S-ICD. One hundred such outpatients were enrolled in the study. Surface rhythm strips were recorded along the sensing vectors of the S-ICD system and the screening template applied. Clinical and standard ECG characteristics of patients who failed the test were compared to those who passed.


Patients had the following characteristics: 72% male, age 57 ± 16 years, body mass index 29 ± 6 kg/m(2), left ventricular ejection fraction 43% ± 17%, QRS duration 109 ± 23 ms, QTc interval 447 ± 39 ms, 44% had coronary disease, and 55% had heart failure. Among the 100 patients, 8% failed the screening test. There were no differences in patient clinical characteristics and most standard ECG measurements. However, patients with T-wave inversions in standard ECG leads I, II, and aVF had a 45% chance of failing.


Eight percent of potential S-ICD patients were not eligible for the S-ICD after failing the screening test designed to identify patients susceptible to T-wave oversensing. Patients with T-wave inversions in leads I, II, and aVF on a standard ECG were 23 times more likely to fail. More work is needed in S-ICD sensing algorithms to increase patient eligibility for the S-ICD.


Defibrillator screening; Implantable cardioverter-defibrillator; Inappropriate shocks; Subcutaneous implantable cardioverter-defibrillator; T-wave oversensing

[Indexed for MEDLINE]

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