Electrocardiographic changes after implantation of a left ventricular assist device - Potential implications for subcutaneous defibrillator therapy.

BACKGROUND: Implantation of a left ventricular assist device (LVAD) leads to a diverse spectrum of changes on the twelve-lead surface electrocardiogram (ECG). We aimed to elucidate the changes of the surface ECG in patients after LVAD implantation potentially impacting ECG based screening tests of subcutaneous implantable cardioverter-defibrillators (S-ICD). METHODS: Patients from 2005 until 2017 with a documented twelve-lead ECG before and after LVAD implantation were included. Baseline parameters were obtained through hospital records. The twelve-lead ECGs registered before and after LVAD implantation were analyzed. RESULTS: From 415 patients undergoing an LVAD implantation, complete datasets were available for 253 patients. 216 patients (85%) were male. Mean age at time of LVAD implantation was 54.7 ±â€¯12.4 years. The underlying etiology was ischemic cardiomyopathy in 119 (47%), dilated cardiomyopathy in 112 (44%), myocarditis in 8 (3%) and other in 14 (6%). We observed a reduction in the amplitude of the R wave in lead I (p < 0.0001), lead II (p < 0.0001), lead III (p < 0.004), lead aVL (p < 0.001) and lead aVF (p < 0.0001) as well as of the S wave in lead III (p < 0.001) and lead aVR (p < 0.0001) after LVAD implantation. We also noticed a reduction of the R:T ratio in lead I (p < 0.0001) as well as in lead II (p = 0.100) and lead aVF (p = 0.292) although statistically non-significant. CONCLUSION: LVAD implantation leads to significant alterations of the surface ECG, especially the R:T ratio in leads I, II and aVF. These leads correlate with the vectors of the ECG based S-ICD screening test. Thus, these ECG changes may impact the continuous eligibility for subcutaneous ICD therapy in patients after LVAD implantation.

Ablation of typical right atrial flutter in patients with pulmonary hypertension.

BACKGROUND: RF ablation for cavotricuspid isthmus (CTI) dependent flutter is an established therapy. Right atrial hypertrophy and enlargement are associated with the occurrence of cavotricuspid isthmus dependent flutter. Therefore, patients with pulmonary hypertension (PAH) are prone to atrial arrhythmias like cavotricuspid isthmus dependent flutter. However, the influence of PAH on typical atrial flutter ablation procedure has not been systematically examined. METHODS: In a retrospective single-centre analysis data of patients undergoing an ablation procedure for cavotricuspid isthmus dependent flutter between January 2007 and October 2009 at Hannover Medical School, Germany were analysed. Only procedures performed by experienced electrophysiologists with an 8mm RF-ablation catheter were included. Data for 196 patients were analysed. Thirty-eight patients were identified with PAH and were compared to 158 patients without PAH for procedural ablation parameters, procedure time, ablation time, ablation points and fluoroscopy time. RESULTS: A bidirectional block of the CTI was achieved in all patients. Patients with severe PAH had a significantly longer procedure time (78±40 min vs. 62±29 min; p=0.033), total ablation time (20±11 min vs. 15±9 min; p=0.02) and more ablation lesions (26±16 vs. 19±12; p=0.018) as compared to patients without PAH. CONCLUSION: Cavotricuspid isthmus dependent flutter ablation in patients with PAH is associated with longer procedure duration and a greater amount of cumulative tissue ablation needed to achieve bidirectional block of the CTI compared to patients without pulmonary hypertension.

Left ventricular assist improves autonomic imbalance in patients with persistent myocardial dysfunction.

BACKGROUND: Left ventricular assist devices (LVAD) are an effective therapeutic option for end-stage heart failure (HF). Reduced heart rate variability (HRV) as a result of autonomic derangement is evident in chronic heart failure and several studies have established the independent prognostic value of HRV in chronic heart failure. OBJECTIVE: In the present study we investigated whether autonomic function is restored in patients after LVAD implantation with persistent, severely depressed left ventricular function. METHODS: Ambulatory Holter ECG recordings were collected in heart failure patients with an LVAD (n=8) und age-matched heart failure patients without an LVAD (n=7) both on optimal medical therapy. Cardiac dimensions and function were assessed by echocardiography or angiography. RESULTS: Analysis for heart rate variability revealed reduced SDNN (67±4 ms), SDANN (56±4 ms) and triangular index (18±1) in heart failure patients on optimal medical therapy. However patients with LVAD demonstrated a restoration in heart rate variability with normal SDNN (108±9 ms), SDANN (103±8 ms) and triangular index (29±2). Compared to patients without LVAD this difference was statistically significant (p<0.01). CONCLUSIONS: In end-stage heart failure patients autonomic imbalance indicated by severely reduced heart rate variability is restored after LVAD implantation with unloading of the failing heart.

Cryoballoon pulmonary vein isolation temporarily modulates the intrinsic cardiac autonomic nervous system.

PURPOSE: Modulation of the intrinsic cardiac autonomic nervous system (ICANS) has been described to occur during radiofrequency pulmonary vein (PV) isolation for paroxysmal atrial fibrillation (AF) and has been controversially proposed to increase clinical success. Energy source used for PV isolation might influence ICANS modulation. The effect of balloon-delivered cryoenergy on the ICANS is unknown. We conducted a study investigating acute periprocedural effect on ICAN as well as changes in heart rate variability (HRV) for standard deviation of normal-to-normal intervals (SDNN) and triangular index (TI) as surrogates for ICANS modulation after cryoballoon PV isolation. METHODS: Fourteen consecutive patients without structural heart disease underwent cryoballoon PV isolation for paroxysmal atrial fibrillation. Acute changes in heart rate requiring pacing during the procedure were recorded. HRV was tested by Holter ECG for SDNN and TI before ablation and after 1 week, 1 month, and 3 months following ablation. RESULTS: Fifty-five out of 56 PV were isolated (98%) with short-term 6-month freedom from paroxysmal AF of 64% by one single procedure. Five patients (36%) showed significant bradycardia during balloon thawing requiring temporary pacing. HRV decreased significantly immediately after PV isolation for both SDNN and TI until 1 month, gradually normalizing toward 3 months follow-up. HRV modulation was not different between patients with or without AF recurrences. CONCLUSIONS: Cryoballoon PV isolation significantly modulates the ICANS, but only temporarily for up to 3 months, measured by HRV changes after ablation.

A prospective experience with the lead integrity alert: new certainties and new uncertainties.

Lead fracture is one of the major complications in implantable cardioverter defibrillator (ICD) therapy often leading to a series of inadequate shocks and thus greatly impairing quality of life of patients. The novel lead integrity alert algorithm by Medtronic (Medtronic Inc., Minneapolis, MN, USA) is addressing this problem. We report a case of a lead failure being correctly predicted by shifting lead impedances about 4 weeks before the first episode of oversensing. Additionally, our case illustrates the new problem of how to clinically handle a patient with a highly probable, but not completely certain, ICD-lead failure.

Morphology of current of injury does not predict long term active fixation ICD lead performance.

BACKGROUND: Currents of injury (COI) have been associated with improved lead performance during perioperative measurements in pacemaker and ICD implants. Their relevance on long term lead stability remains unclear. METHODS: Unipolar signals were recorded immediately after active fixation ICD lead positioning, blinded to the implanting surgeon. Signals were assigned to prespecified COI types by two independent investigators. Sensing, pacing as well as changes requiring surgical intervention were prospectively investigated for 3 months. RESULTS: 105 consecutive ICD lead implants were studied. All could be assigned to a particular COI with 48 type 1, 43 type 2 and 14 type 3 signals. Pacing impedance at implant was 703.8+/-151.6 Ohm with a significant COI independent drop within the first week. Sensing was 10.6mV+/- 3.7mV and pacing threshold at implant was 0.8+/-0.3mV at 0.5ms at implant. There was no significant difference between COI groups at implant and during a 3 months follow up regarding sensing, pacing nor surgical revisions. CONCLUSIONS: Three distinct patterns of unipolar endocardial potentials were observed in active fixation ICD lead implant, but COI morphology did not predict lead performance after 3 months.

Reduced delayed rectifier K+ current, altered electrophysiology, and increased ventricular vulnerability in MLP-deficient mice.

BACKGROUND: Mice with a knockout (KO) of muscle LIM protein (MLP) exhibit many morphologic and clinical features of human cardiomyopathy. In humans, MLP-expression is downregulated both in ischemic and dilative cardiomyopathy. In this study, we investigated the effects of MLP on the electrophysiologic phenotype in vivo and on outward potassium currents. METHODS AND RESULTS: MLP-deficient (MLPKO) and wild-type (MLPWT) mice were subjected to long-term electrocardiogram (ECG) recording and in vivo electrophysiologic study. The whole-cell, patch-clamp technique was applied to measure voltage dependent outward K+ currents in isolated cardiomyocytes. Long-term ECG revealed a significant prolongation of RR mean (108 +/- 9 versus 99 +/- 5 ms), P (16 +/- 3 versus 14 +/- 1 ms), QRS (17 +/- 3 versus 13 +/- 1 ms), QT (68 +/- 8 versus 46 +/- 7 ms), QTc (66 +/- 6 versus 46 +/- 7 ms), JT (51 +/- 7 versus 34 +/- 7 ms), and JTc (49 +/- 5 versus 33 +/- 7 ms) in MLPKO versus MLPWT mice (P < .05). During EP study, QT (80 +/- 8 versus 58 +/- 7 ms), QTc (61 +/- 6 versus 45 +/- 5 ms), JT (62 +/- 9 versus 43 +/- 6 ms), and JTc (47 +/- 5 versus 34 +/- 5 ms) were also significantly prolonged in MLPKO mice (P < .05). Nonsustained VT was inducible in 9/16 MLPKO versus 2/15 MLPWT mice (P < .05). Analysis of outward K+ currents in revealed a significantly reduced density of the slowly inactivating outward K+ current IK, slow in MLPKO mice (11 +/- 5 pA/pF versus 18 +/- 7 pA/pF; P < .05). CONCLUSION: Mice with KO of MLP exhibit significant prolongation of atrial and ventricular conduction and an increased ventricular vulnerability. A reduction in repolarizing outward K+ currents may be responsible for these alterations.