Arrhythmia discrimination by physician and defibrillator: importance of atrial channel.
BACKGROUND
Many ICD carriers experience inappropriate shocks, but the relative merits of dual- /single-chamber devices for arrhythmia discrimination still remain unclear. We explored possible advantages of the atrial data provided by dual-chamber implantable defibrillators (ICD) for discrimination of real-life supraventricular/ventricular tachyarrhythmias (SVT/VT).


METHODS
100 dual-chamber traces from 24 ICD were blindly reviewed in dual-chamber and simulated single-chamber (with/without discriminator data) reading modes by five electrophysiologists who determined chamber of origin and provided Likert-scale "confidence" ratings. We assessed 1) intra/interobserver concordance; 2) diagnostic accuracy, using expert diagnoses as a reference standard; 3) ROC curves of sensitivity/specificity of "likelihood perception" scores, generated by combining chamber-of-origin diagnostic judgments with Likert-scale "confidence" ratings. We also assessed diagnostic accuracy of automated discrimination by all possible dual-/single-chamber algorithm configurations.


RESULTS
Interobserver concordance was "substantial" (modified Cohen kappa-test values for dual-/single-chamber, 0.79/0.68); intraobserver concordance "almost complete" (kappa ≥ 0.89). Dual-chamber mode provided best diagnostic sensitivity/specificity (99%/92%) and highest reader confidence (p<0.001). Area under ROC curves of sensitivity/specificity values for the "likelihood perception" score (representing electrophysiologists' perceptions of the likelihood that an episode was of ventricular origin) was highest in dual-chamber mode (0.98 vs. 0.93 for both single-chamber modes; p<0.001). Regarding automated discrimination, all four dual-chamber configurations conferred 100% sensitivity (specificity values ranged 39%-88%), whereas single-chamber configurations appeared inferior (best sensitivity/specificity combination, 89%/64%).


CONCLUSIONS
Availability of the atrial channel helps in reducing inappropriate ICD therapies by providing relevant advantages in terms of both appropriate cardiologist's post-hoc discrimination of SVT/VT (improving program tailoring) and automated arrhythmia discrimination.
Institute of Cardiology, University of Bologna, Azienda Ospedaliera S.Orsola-Malpighi, Bologna, Italy. igor.diemberger@gmail.com
Igor
I
Diemberger
Cristian
C
Martignani
Mauro
M
Biffi
Lorenzo
L
Frabetti
Cinzia
C
Valzania
Robin M T
RM
Cooke
Claudio
C
Rapezzi
Angelo
A
Branzi
Giuseppe
G
Boriani
D000368:Aged; D000465:Algorithms; D002309:Cardiology / Q000592:standards* / Q000706:statistics & numerical data; D016208:Databases, Factual; D017147:Defibrillators, Implantable / Q000592:standards* / Q000706:statistics & numerical data; D004562:Electrocardiography / Q000295:instrumentation / Q000592:standards* / Q000706:statistics & numerical data; D006325:Heart Atria; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013617:Tachycardia, Supraventricular / Q000175:diagnosis*; D017180:Tachycardia, Ventricular / Q000175:diagnosis*