Hypoplastic right lung associated with right pulmonary vein stenosis and systemic collateral.

We present a case of a 6-month-old girl diagnosed as unilateral pulmonary vein stenosis (right inferior pulmonary vein) with dextroposition of the heart, hypoplastic right lung, hypoplastic right pulmonary artery, collateral from the descending aorta supplied right lower lung, connection between collateral and right pulmonary artery with retrograde flow from right pulmonary artery into main pulmonary artery, and right superior and middle pulmonary vein agenesis. A combined modality of imaging including chest film, echocardiography, multidetector computerized tomography, and the cardiac catheterization nicely demonstrated all of the unique and rare congenital abnormalities.

Counter intuitive relations between in vivo RF lesion size, power, and tip temperature.

BACKGROUND: Radiofrequency (RF) lesion size in vitro is positively correlated with applied power and catheter tip temperature. However, the relation between RF lesion size, power, and tip temperature in vivo remains unclear. We hypothesized that due to flow, anatomy and tip contact effects in vivo, increased tip temperature would be inversely related to applied power and RF lesion size. METHODS: RF lesions were created on the endocardium of 16 pigs using 5, 6, and 7 Fr catheters. The ablation generator was set to achieve a temperature of 70 degrees C. RF lesions were created in different regions of the heart so as to encompass a wide range of blood flow and catheter movement conditions. RF lesions were measured acutely (DIMEN, mm) and correlated with average power applied (POWER, W), and average tip temperature (TEMP, degrees C). The POWER and TEMP relation was also examined. RESULT: For TEMPs below 55 degrees C, the power output from the generator was typically maximized at 50 W. At TEMPs above 55 degrees C, POWER decreased exponentially with increasing TEMP (POWER = 50 - exp(-((41-TEMP)/7)), r = 0.98, p < 0.05). Further, DIMEN tended to be inversely related to TEMP (Slope: -0.07 +/- 0.04, r = -0.15, p = 0.07); but, was positively related to POWER (Slope: 0.04 +/- 0.02, r = 0.23, p < 0.05). These relations varied by tip size and estimated local blood flow characteristics. CONCLUSION: In vivo, variable tissue contact and flow yield DIMEN-POWER-TEMP relations opposite to those found in vitro. These counterintuitive results suggest that maximum in vivo RF lesion size is achieved when power is maximized at tip temperatures between 50 and 60 degrees C.

Bidirectional ventricular tachycardia and channelopathy.

Based on similarity of electrocardiographic features, bidirectional ventricular tachycardia has been considered a variant of long QT syndrome. Genes causing long QT syndrome were used as candidate genes in 4 patients with bidirectional ventricular tachycardia. In 2 patients, we identified a common low penetrance HERG allele (R1047L) with an intermediate biophysical phenotype.

Catheter tip cooling during radiofrequency ablation of intra-atrial reentry: effects on power, temperature, and impedance.

INTRODUCTION: Cooling the catheter tip either passively with increased tip size or actively during radiofrequency catheter ablation (RFCA) has been shown in canine thigh preparations to create larger lesions than standard catheter tips, yielding a theoretical advantage for improving the outcome of RFCA for intra-atrial reentrant tachycardia (IART). METHODS AND RESULTS: The pediatric RFCA database at the Medical University of South Carolina was reviewed for RFCA of IART in patients with structural heart disease. From a total of 31 patients who underwent procedures during the study period, 8 patients in whom ablation with conventional ablation techniques failed and who went on to passive cooling with an 8-mm tip catheter or active cooling with an internally cooled-tip catheter were studied. Power delivery was greater but temperature and impedance were lower during cooled ablation than during conventional ablation. Passive cooling was associated with higher power than active cooling. These changes in RF biophysical characteristics were associated with successful elimination of 11 of 13 IART circuits in 7 of 8 patients. CONCLUSION: Cooling during RF ablation of atrial tachycardia clearly yielded greater power delivery in vivo and was associated with success.

Complete elimination of incessant polymorphic ventricular tachycardia in an infant with MIDAS syndrome: use of endocardial mapping and radiofrequency catheter ablation.

Experience with radiofrequency catheter ablation of ventricular tachycardia (VT) in pediatric patients is limited. A 5-month-old white female infant (body weight 5.5 kg) with MIDAS syndrome who suffered from incessant polymorphic VT (ventricular rates 250 to 300 beats/min) and was unresponsive to medical treatment resulting in significantly depressed left ventricular (LV) function underwent a total of four catheter ablation procedures during a 5-month period. Each of the procedures reduced the number of morphologies and the rate of the tachycardia, but VT returned after each of the first three procedures, despite concomitant medical therapy. Activation mapping and pace mapping were used to identify the anatomic substrates, which were found at different locations at the LV septum and LV free wall. All forms of VT finally were ablated successfully. There were no significant complications. After the fourth procedure, the patient was in continuous sinus rhythm. Follow-up examination 29 months after the last procedure while the child was not taking any medication showed normal sinus rhythm and normal LV function. This report demonstrates the usefulness and safety of radiofrequency catheter ablation in an infant with polymorphic VT who was unresponsive to medical therapy.