Potassium channel blockers are sometimes effective in the rhythm management of persistent atrial fibrillation. However, on rare occasions, a life-threatening episode of torsade de pointes develops during treatment with these agents. Among several precautions against this tragedy, preventing exaggerated QT prolongation is of paramount importance. One of the difficulties in monitoring the QT interval during atrial fibrillation is the fact that its length varies depending not only on the fluctuating preceding intervals, but on other factors such as neurohumoral activation. In fact, even at the same preceding RR interval, the QT interval may vary from day to night, between atrial fibrillation and sinus rhythm. Accordingly, the QTc interval may not be a reliable parameter for predicting proarrhythmic events. As the result, close monitoring of the QT interval itself, just like INR monitoring during warfarin treatment, is mandatory both before and during treatment with these agents.

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Background: The effects of upgrading from right ventricular (RV) pacing to cardiac resynchronization therapy (CRT) in patients with heart failure remains unclear. The aim of this study was to evaluate the improvement of cardiac function in patients upgraded from RV pacing to CRT.
Methods: We studied 48 consecutive patients who underwent CRT implantation, and were followed up for more than 6 months. This group included 15 patients who were upgraded from RV pacing. We measured left ventricular (LV) dp/dt to determine the timing of LV-RV sequential pacing. Echocardiographic examination was performed before and 6–12 months after the CRT procedure to assess the LV ejection fraction (LVEF).
Results: In overall patients, LVEF increased after CRT (31.4±9.8 vs. 37.1±13.6%, p=0.005). The increase of LVEF was more significant in the upgrade group (31.3±9.4% to 41.9±13.9%, p=0.01) than in the newly implanted group (31.5±10.1% to 35.0±13.1%, p=0.13). An increase of dp/dt during CRT was significantly positively associated with an increase of LVEF (r=0.74, p=0.01) in overall patients.
Conclusion: The upgrading from RV pacing to CRT was associated with greater improvement of LV systolic function than de novo CRT implantation. The change of dp/dt might be useful to predict the improvement of LV systolic function.

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Introduction: Previous studies have shown that atrial fibrillation (AF) recurrence after pulmonary vein (PV) isolation depends on various factors; however, the effect of cigarette smoking on AF recurrence after PV isolation has not been investigated.
Methods and Results: Fifty-nine consecutive patients with drug-refractory AF (48 men and 11 women, mean age: 60±11 years) who underwent PV isolation were included. The patients were divided into two groups: the non-smoker group, i.e., “never smokers (n=29),” and the smoker group consisting of 30 patients who were either “former smokers (n=15)” or “current smokers (n=15)”. The diameter of all four PVs and the left atrial volume tended to be larger in the smoker group. During the mean follow-up period of 306±95 days, the AF recurrence rate was higher in the smoker group than in the non-smoker group (43% vs. 14%, p<0.05). The relative risk of AF recurrence associated with smoking was 3.19 (95% CI 1.23 to 8.27, p=0.017). The AF recurrence rate was increased in both current smokers (40%) and former smokers (47%) compared to never smokers (14%).
Conclusions: AF recurrence after PV isolation was significantly higher in the smoking patients. The substrate of AF may be worsened by exposure to cigarette smoking.

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There is little information on venous patency after pacing leads are inserted in veins during pacemaker or implantable cardioverter defibrillator (ICD) implantation. Herein we present a report on venous patency during the immediate postoperative period after permanent pacemaker or ICD implantation.
Subjects and Methods: Twenty-five patients underwent a permanent pacemaker or ICD implantation by venous puncture method, and venography was performed 1 week later. We assessed the pacemaker-implantation side, approach used, implanted device, number of implanted leads, and clinical symptoms.
Results: Narrowing of the vein was found in 14 patients (56%), including 7 patients (28%) with occlusion. Stenosis and occlusion were seen more in patients with left-sided implantation than those with right-sided implantation (71% vs. 25%, P<0.05). ICD implantation was more frequently associated with venous stenosis or occlusion than pacemaker implantation (65% vs. 37.5%, P<0.05). The approach used and the number of leads implanted did not correlate with venous stenosis or occlusion. Six of the 7 patients who developed complete occlusion showed clinical symptoms.
Conclusion: Thrombus formation after pacemaker implantation can occur in the acute stage within 1 week. The incidence of venous stenosis or thrombus formation was higher with left-sided implantation and ICD.

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A 34-year-old man with a surgically repaired Tetralogy of Fallot complained of palpitation, fatigue, and presyncope. A 12-lead ECG showed atrial tachycardia with a cycle length of 250 ms and a P wave morphology positive in leads II, III and aVF, and negative in lead V1. Although the EnSite system (version 6.0J) made use of noncontact mapping to delineate the counterclockwise reentry around the crista terminalis, it was difficult to rule out the incisional atrial reentry because the location of the surgical incision was far from the multi-electrode array. Since the bipolar contact mapping of the EnSite system revealed the location of the atriotomy incision, entrainment mapping during the tachycardia demonstrated the critical reentry circuit around the crista terminalis. Radiofrequency ablation targeting the critical isthmus from the lower position of the crista terminalis to the posterior dense scar which was continuous with the inferior vena cava, and to the atriotomy scar, eliminated the tachycardia.

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The case of a patient with narrow QRS tachycardia is herein presented. During an electrophysiological study, this tachycardia was diagnosed as a focal atrial tachycardia with a high sensitivity to adenosine-5′-triphosphate (2 mg), and originating from near the His-bundle region. We could not ablate the earliest activation site in the right atrium because of the simultaneous recording of the His potential. The radiofrequency applications in the right atrium around the earliest activation site failed to terminate the tachycardia. Subsequent attempt of radiofrequency application in the non-coronary aortic cusp, where the earliest atrial activation without His potential was obtained, successfully eliminated the tachycardia without any atrioventricular nodal injury.

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A 65 year-old female was admitted to our hospital because of syncope. She has been previously diagnosed with dilated cardiomyopathy. Twelve-lead electrocardiogram (ECG) presented narrow QRS tachycardia. Electrophysiological study and radiofrequency catheter ablation was performed. Under isoproterenol infusion, supraventricular tachycardia (SVT) was easily induced followed by critical AH interval. The mechanism of SVT was diagnosed with slow-fast atrioventricular nodal reentrant tachycardia (AVNRT). We tried slow-pathway ablation from venous approach targeted at the triangle of Koch using electrogram guide and anatomical approach. Slow-pathway conduction was not eliminated, however, and SVT still could be easily induced. Therefore we delivered radiofrequency (RF) from the left atrial (LA) septum by transseptal approach using an electro-anatomical mapping (EAM) system. After RF application at mid-septum from the LA, the slow-pathway conduction was modified and SVT could not be induced.

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We report the outcome of the iliac vein approach for permanent pacemaker implantation in 4 patients in whom the conventional pectoral approach was not possible. The reasons for using the iliac vein approach were: recurrent lead infections at bilateral pectoral positions in 1 patient; superior vena cava obstruction following cardiac surgery in 2 patients; and a postoperative dermal scar due to right radical mastectomy secondary to a persistent left superior vena cava with absence of the innominate vein in 1 patient. This technique was safe and effective during the mean follow-up period of 24.3 months. At the latest follow-up, no patients showed signs of electrophysiological abnormalities. No short- or long-term complications were seen. Conclusions: The iliac vein approach is a less invasive and more feasible alternative without any complications for patients in whom the pectoral approach cannot be used.

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This report presents the case of a 60-year-old female who demonstrated sick sinus syndrome after a single administration of Garenoxacin (GRNX). She was administered GRNX for an upper respiratory infection and 10 minutes thereafter, she suddenly felt palpitation and numbness of both arms. She was transferred to the hospital 2 hours after taking GRNX. An electrocardiogram showed bradycardia with junctional escape beats and the longest sinus arrest was 4 seconds. She was treated with a temporary pacemaker and 21 hours after the administration of GRNX her sinus node function was observed to have completely improved. GRNX-induced sick sinus syndrome was suspected because her clinical course was compatible with the concentration of GRNX and her other cardiological assessments, including an electrophysiologic study (EPS) which were conducted on the 9^th day of the admission, were normal. GRNX has less effect on the QT interval than other quinolone agents. However, physicians should be aware of the risk of sick sinus syndrome because GRNX is frequently prescribed in outpatient clinics.

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