Yaman, Malek M. El

Background: Although multiple macroreentrant atrial flutters are seen in postoperative patients with congenital heart disease, cavotricuspid isthmus (CVTI) dependent flutter remains a fairly common arrhythmia in this group. When a Fontan or atrial switch (Mustard/Senning) type of procedure is performed, a portion of the CVTI is excluded from catheter access obtainable via a systemic venous route. We evaluated different techniques to access this excluded portion and completely ablate CVTI dependent flutter. Methods/Results: Between 1990 and 2007, 140 patients with surgically corrected congenital heart disease underwent an ablation procedure at our institution. Their records were reviewed to identify those with prior Fontan or atrial switch procedure who had documented CVTI dependent flutter requiring ablation. Data collected included methods of catheter access, circuits observed or induced, the location and number of ablation lines, immediate and long-term success, and complications. Results: Sixteen patients were identified (14, Fontan; 2, Mustard). In 12/16 (75%) patients bidirectional block of CVTI dependent flutter could not be achieved by right atrial (venous approach) ablation alone. In 7 of those, the excluded portion of the CVTI was targeted for ablation. This was accomplished by a retrograde transaortic approach via an interventricular communication then through the right atrioventricular valve (5 patients). Another retrograde transaortic approach was used with the catheter crossing the left atrioventricular valve then an atrial septal communication (one patient). A third approach involved an antegrade transconduit puncture (one patient). In all 7 patients, successful ablation of CVTI dependent flutter with bidirectional block was achieved. Post-procedure, one patient had temporary AV block requiring pacemaker placement. Follow-up was available on 4/7 patients (3 to 22 months, mean 10 months) with no documented recurrence of their CVTI dependent flutter. Conclusion: Even when surgical procedures exclude a portion of the CVTI, complete ablation for typical atrial flutter with resulting bidirectional block can be achieved via “non-traditional” approaches targeting the surgically excluded arrhythmogenic tissue.

Long QT syndrome (LQTS) is a heterogeneous group of channelopathies characterized by increased risk of potentially lethal ventricular arrhythmias. LQT1, LQT2, and LQT3 comprise 95% of genetically proven cases and exhibit a number of established genotype-phenotype correlations. The study aimed at examining the phenotypes of genotype-negative LQTS, accounting for ~25% of LQTS cases. An IRB-approved retrospective analysis was conducted on 56 patients (39 female, 25 ± 17 years) who, after genetic testing either in our sudden death genomics laboratory or with the commercially available Familion test, were negative for mutations in the 3 principal LQTS-susceptibility genes ( KCNQ1, KCNH2, and SCN5A), and the minor genes underlying LQT5 and LQT6. All had been diagnosed with LQTS, with a clinical diagnostic score of ≥ 3.5 or QTc ≥ 480 ms. The mean diagnostic score was 4.4 (95% CI 4.2 – 4.7); mean QTc was 525 ms (95% CI 508 – 543 ms). Two-thirds were symptomatic (syncope, cardiac arrest, and/or seizures) with exercise-triggered events in 10 (26%). Twenty-one (38%) had a family history of sudden cardiac arrest. ECG showed a T wave pattern suggestive of LQT1 in 32%, LQT2 in 43%, and LQT3 in 18%. In those with exercise-induced symptoms, the ECG was LQT2-like in 50% and LQT1-like in 30%. One patient had post-partum syncope with an LQT2-like ECG. None had an auditory trigger, but 3 patients, all with an LQT2-like ECG, had a family history of auditory-triggered events. One-third of the patients had received an ICD, 58% as secondary prevention. Over 2/3 were on beta-blockers. Among the 45 patients so far tested for mutations in minor LQTS-susceptibility genes, 2 had LQTS-causing mutations in ANKB (LQT4), 1 in SCN4B (LQT10), 1 in AKAP9 (LQT11) and 2 in SNTA1 (LQT12). Genotype-negative patients with a firm LQTS diagnosis show marked phenotypic heterogeneity, suggesting multiple underlying pathogenic pathways. Only a few patients have LQTS-causing mutations in minor genes after complete LQT1–12 genetic testing. Classifying genotype negative patients into LQT1-, LQT2-, or LQT3-like profiles may guide the discovery of novel genes encoding channel interacting proteins corresponding to those specific signaling pathways.