A 38-year-old male with a mechanical aortic valve implanted 15 years ago for rheumatic disease presented to the hospital with sudden cardiopulmonary collapse. Upon arrival, he was in shock on high-dose pressors, intubated and mechanically ventilated. Chest radiograph revealed marked pulmonary oedema, and known mechanical valve was not well visualized on the film. A transthoracic echocardiogram showed severe turbulence across the left ventricular outflow tract, severe aortic regurgitation, and the known mechanical valve could not be visualized. A tomogram showed the mechanical valve in the distal aortic arch (Panels A and B). The patient was immediately taken to the operating room. Emergency re-operative sternotomy was done expeditiously. Cardiopulmonary bypass (CPB) was initiated and the patient was cooled to allow for circulatory arrest. With an arrested circulation, the aortic arch was opened via an anterior aortotomy, the embolized mechanical valve explanted, and debris removed (Panels C and D...

Cardiovascular Implantable Electronic Device Implantation with Uninterrupted DabigatranBackgroundWhile continuation of oral anticoagulation (OAC) with warfarin may be preferable to interruption and bridging with heparin for patients undergoing cardiovascular implantable electronic device (CIED) implantation, it is uncertain whether the same strategy can be safely used with dabigatran.Objective and MethodsTo determine the risk of bleeding and thromboembolic complications associated with uninterrupted OAC during CIED implantation, replacement, or revision, the outcomes of patients receiving uninterrupted dabigatran (D) were compared to those receiving warfarin (W).ResultsD was administered the day of CIED implant in 48 patients (age 66 ± 12.4 years, 13 F and 35 M, 21 ICDs and 27 PMs), including new implant in 25 patients, replacement in 14 patients, and replacement plus lead revision in 9 patients. D was held the morning of the procedure in 14 patients (age 70 ± 11 years, 4 F and 10 M, 5 ICDs and 9 PMs). W was continued in 195 patients (age 60 ± 14.4 years, 54 F, and 141 M), including new implant in 122 patients, replacement in 33 patients, and replacement plus lead revision or upgrade in 40 patients. Bleeding complications occurred in 1 of 48 patients (2.1%) with uninterrupted dabigatran (a late pericardial effusion), 0 of 14 with interrupted D, and 9 of 195 patients (4.6%) on W (9 pocket hematomas), P = 0.69. Fifty percent of bleeding complications were associated with concomitant antiplatelet medications.ConclusionsThe incidence of bleeding complications is similar during CIED implantation with uninterrupted D or W. The risks are higher when OAC is combined with antiplatelet drugs.

External mechanical forces can cause ventricular capture and fibrillation (i.e., commotio cordis). In animals, we showed that chest compressions (CCs) can also cause the phenomenon. The aim of the present study was to determine whether ventricular capture by CCs occurs in humans. Electronic rhythm strips were analyzed in 31 cases of out-of-hospital cardiac arrest. The timing of the CCs was identified from the changes in thoracic impedance between the defibrillator pads. Ventricular capture was defined as QRS complexes of similar morphology occurring intermittently but synchronized with the CC artifact and impedance waveform. Only intermittent ventricular capture was identified to avoid misclassifying constant motion artifacts or intrinsic rhythm as ventricular capture. Of the 29 patients who received CCs for >= 1 minute, minimal or stable motion artifact was present in 24. Intermittent ventricular capture was found in 7 of the 24 patients. In the patients with ventricular capture, the number of ventricular activations (from ventricular capture and native beats) was greater during the CCs than when the CCs was not being performed (18 +/- 8.9 vs 9.7 +/- 4.0 activations in 15 seconds, p = 0.01). However, in patients without ventricular capture, they were similar (6.8 +/- 8.2 vs 7.2 +/- 8.8 activations in 15 seconds, p = 0.47). Refibrillation occurred in 22 patients; it began during the CCs in 16 and closely following their initiation in 3. In conclusion, CCs during cardiopulmonary resuscitation can electrically stimulate the heart. Additional studies evaluating, the effect of ventricular capture on cardiopulmonary resuscitation outcomes, its relation to refibrillation, and methods to prevent or time ventricular capture by CCs are warranted. (C) 2012 Elsevier Inc. All rights reserved. (Am J Cardiol 2012;109:670-674)

Periods of Highly Organized Activation During VF Background: Little is known about long‐duration ventricular fibrillation (LDVF), lasting 1–10 minutes when resuscitation is still possible. Methods and Results: To determine global left ventricle (LV) endocardial activation during LDVF, 6 canines (9.5 ± 0.8 kg) received a 64‐electrode basket catheter in the LV, a right ventricular (RV) catheter, and a 12‐lead electrocardiogram (ECG). Activation sequences of 15 successive cycles after initiation and after 1, 2, 3, 5, 7, and 10 minutes of LDVF were determined. Early during VF, LV endocardial activation was complex and present throughout most (78.0 ± 9.7%) of each cycle consistent with reentry. After 3–7 minutes of LDVF in 5 animals, endocardial activation became highly synchronized and present for only a small percentage of each cycle (18.2 ± 7.7%), indicating that LV endocardial reentry was no longer present. During this synchronization, activations arose focally in Purkinje fibers and spread as large wavefronts to excite the Purkinje system followed by the subendocardial working myocardium. During this synchronization, the ECG continued to appear irregular, consistent with VF, and LV cycle length (183 ± 29 ms) was significantly different than RV cycle length (144 ± 14 ms) and significantly different than the LV cycle length when synchronization was not present (130 ± 11 ms). Conclusion: After 3–7 minutes of LDVF, a highly organized, synchronous, focal LV endocardial activation pattern frequently occurs that is not consistent with reentry but is consistent with triggered activity or abnormal automaticity in Purkinje fibers. The ECG continues to appear irregular during this period, partially because of differences in LV and RV cycle lengths. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1266‐1273, November 2010)

BACKGROUND While reentry within the ventricular myocardium (VM) is responsible for the maintenance of short-duration ventricular fibrillation (SDVF; VF duration <1 minute), Purkinje fibers (PFs) are important in the maintenance of long-duration ventricular fibrillation (LDVF; VF duration >1 minute).OBJECTIVE The purpose of this study was to test the hypothesis that the mechanisms of defibrillation may also be different for SDVF and LDVF.METHODS A multielectrode basket catheter was deployed in the left ventricle of eight beagles. External defibrillation shocks were delivered with a ramp-up protocol after SDVF (20 seconds) and LDVF (150 seconds). Earliest VM and PF activations were identified after the highest energy shock that failed to terminate VF and the successful shock.RESULTS Defibrillation was successful after 36 +/- 12 and 181 +/- 14 seconds for SDVF and LDVF, respectively. The time after shock delivery until earliest activation was detected for failed shocks and was significantly longer after LDVF (138.7 +/- 24.1 ms) than after SDVF (75.6 +/- 8.7 ms). Earliest postshock activation after SDVF typically initiated in the VM (14 of 16 episodes), while it always initiated in the PF (16 of 16 episodes) after LDVF. Sites of earliest activity during sinus rhythm correlated with sites of earliest postshock activation for PF-led cycles but not for VM-led cycles.CONCLUSION Earliest recorded postshock activation is in the Purkinje system after LDVF but not after SDVF. This difference raises the possibility that the optimal defibrillation strategy is different for SDVF and LDVF.

Background: Defibrillation waveforms and strategies have been developed using models of short duration ventricular fibrillation (SDVF). Significant metabolic changes occur after long duration ventricular fibrillation (LDVF) that may play an important role in the mechanisms of defibrillation. The objective of this study was to determine if defibrillation threshold (DFT) or the time to 1st post‐shock activation (PSA) differed after SDVF and LDVF.Methods: A ramp up protocol was used to determine the defibrillation threshold (DFT) of a biphasic waveform in 9 pigs (30–35 kg) and 6 beagles (9–11 kg) after one episode each of SDVF (10 s) and LDVF (150 s). PSA time was recorded by intraventricular catheters in the both ventricles after successful defibrillation shocks.Results: The DFT was higher for pigs after SDVF than LDVF (102±43 J and 79±34, respectively, p<0.05) but was not significantly different for beagles (8.3±1.5 and 13.3±9.3 J, respectively). The majority of the PSA after SDVF were recorded within 170 ms of the shock, (9/9 pigs, 4/6 beagles), while all PSAs after LDVF had a pause of greater than 275 ms.Conclusion: Different times of PSA and a change in DFT in pigs may indicate that there are significant differences in defibrillation after SDVF and LDVF. Further study of defibrillation after LDVF is warranted to determine if strategies and waveforms may be improved for clinically relevant durations of LDVF.

BACKGROUND:During resuscitation, fibrillation often recurs. In swine, we studied refibrillation after long-duration ventricular fibrillation, investigating an association with chest compressions (CCs). METHODS AND RESULTS:In protocol A, 47 episodes of long-duration ventricular fibrillation lasting at least 2.5 minutes were induced in 8 animals. After defibrillation, CCs were required for 35 episodes and delivered with a pneumatic device (Lucas cardiopulmonary resuscitation). In 9 episodes, refibrillation occurred within 2 seconds of CC initiation (group 1) and in 26 episodes, CCs were delivered without refibrillation (group 2). From the ECG and intracardiac electrodes, the RR interval preceding CCs, the shortest cycle length during the first 2 CCs (short), and the preceding cycle length (long) were measured. A similar study was conducted in 3 more animals without intracardiac catheters (protocol B). In protocol A, the mean RR before CC was 665+/-292 ms in group 1 and 769+/-316 in group 2. CCs stimulated ventricular beats in all 35 episodes. The short and long intervals were shorter in group 1 (215+/-31 and 552+/-210 ms) than in group 2 (402+/-153 and 699+/-147 ms) (P=0.009 and P=0.04, respectively). The prematurity index (short/RR) was lower in group 1 than in group 2 (0.35+/-0.09 vs 0.58+/-0.21; P<0.01). A short interval <231 ms predicted refibrillation with 88% sensitivity and 91% specificity. In protocol B, CCs were required in 11 episodes, causing ventricular stimulation in all of them and ventricular fibrillation within the first 2 CCs in 3. CONCLUSIONS:Under some conditions, CC during resuscitation can stimulate the ventricles and initiate ventricular fibrillation by a long-short sequence.

Background: Ventricular capture (VC) by external mechanical forces has been described with precordial thumps and commotio cordis. The force required to electrically stimulate the heart during chest...

Lesion characteristics including size and transmurality are important factors in the creation of conduction block with respect to catheter ablation. The energy required to create safe and effective lesions may vary from one ablation system to another. Understanding the differences in this energy requirement could allow the operator to titrate the appropriate therapy with each system - generating successful outcomes while minimizing complications. Twenty-two swine underwent an acute ablation procedure whereby 4 lesions were placed with a different catheter in each of the following areas: the left atrium (LA), along the cavo-tricuspid isthmus (CVI) and in right atrial tissue (RA). Four ablation catheters were studied: an 8mm cryoablation catheter, an 8mm standard RF catheter, a 2.5mm insulated open irrigated catheter, and a 3.5mm open irrigated RF catheter. Energy was applied for 30s with the RF catheters and 120sec with cryo, within the therapeutic range for that catheter. Lesion size, RF/Cryo characteristics, popping and other adverse events were recorded. One hundred sixty-three lesions were analyzed. There was no statistical difference between the lesion volumes created by each catheter. The lesion characteristics of the catheters are shown in Table 1 . Transmurality ranged from 75–90% with a trend toward greater transmurality with the 2.5mm irrigated catheter group. There was no evidence of tissue popping or other adverse events. These catheters when used within the therapeutic range on average created similar volume lesions but with wide variation. Cryoablation tended to create the largest lesions but was less likely to be transmural, while the 2.5mm catheter was most likely to deliver transmural lesions. Catheter comparison

Background: The distal tip electrode for standard open irrigated catheters is cooled during ablation. While this allows for greater energy delivery to the myocardium relative to a nonirrigated elec...