Circulation: Arrhythmia and Electrophysiology On the Beat March 2018

03/20/18 • 80 min

Circulation: Arrhythmia and Electrophysiology On the Beat

Paul Wang: Welcome to the monthly podcast “On The Beat”, for Circulation: Arrhythmia and Electrophysiology. I am Dr. Paul Wang, Editor-in-Chief, with some of the key highlights from this month's issue. We'll also hear from Dr. Suraj Kapa, reporting on new research from the latest journal articles in the field.

In our first article, Adetola Ladejobi and associates studied 1,433 patients, between 2000 and 2012, who were discharged alive after sudden cardiac arrest. A reversible and correctable cause was identified in 792 patients, or 55%. A reversible cause for sudden cardiac arrest was defined as significant electrolyte or metabolic abnormality, evidence of acute myocardial infarction or ischemia, recent initiation of antiarrhythmic drug, or illicit drug use, or other reversible circumstances.

Of the 792 sudden cardiac arrest survivors, due to reversible or correctable cause, 207 or 26% of the patients received an ICD after their indexed sudden cardiac arrest. During a mean follow-up of 3.8 years, 319 or 40% of patients died. ICD implantation was highly associated with a lower all-cause mortality, p < 0.001, even after correcting for unbalanced baseline characteristics.

In subgroup analyses, only patients with sudden cardiac arrest, were not associated with myocardial infarction, extracted benefit from the ICD, p < 0.001.

The authors concluded that in survivors of sudden cardiac arrest, due to a reversible and correctable cause, ICD therapies associated with lower all-cause mortality, except if the sudden cardiac arrest was due to myocardial infarction.

Further prospect of multi-center randomized control trials will be needed to confirm this observation.

In our next study, Carlo Pappone and associates, studied 81 patients with persistent atrial fibrillation, randomized to undergo high density electrophysiological mapping, to identify repetitive regular activities, before modified circumferential pulmonary vein ablation, or modified circumferential pulmonary vein ablation alone. The primary endpoint was freedom from arrhythmia recurrence at one year.

In the 81 patients with persistent atrial fibrillation, there were 479 regions exhibiting repetitive regular activities in these patients, or 5.9 repetitive regular activities per patient. There were 232 regions in the mapping group, which consisted of 41 patients, and 247 regions in the control group, consisting of 40 patients. Overall, 39% of the repetitive regular activities were identified within pulmonary veins, whereas 61% were identified in non-pulmonary vein regions.

Mapping-guided ablation resulted in higher arrhythmia termination rate, as compared to conventional strategy, 61% vs. 30%, p < 0.007. Total RF duration, mapping, and fluoroscopy times were not significantly different between the groups. No major procedure related adverse events occurred.

After one year, 73% of the mapping group of patients were free of recurrences, compared to 50% of the control group, p = 0.03.

The authors concluded that targeted ablation of regions showing repetitive regular activities provided adjunctive benefit in terms of arrhythmia freedom at one year in treatment of patients with persistent atrial fibrillation. These findings should be confirmed by additional larger randomized multi-centered studies.

In the next article, Maciej Kubala and associates examine repolarization abnormalities in 40 patients with arrhythmogenic right ventricular cardiomyopathy, comparing extent and location of abnormal T-waves of one millimeter or greater in depth, downsloping elevated ST segment in two or more adjacent leads to the area and location of endocardial bipolar and unipolar, and epicardial bipolar voltage abnormalities. They found an abnormal unipolar right ventricular endocardial area of 33.4% with presence in eight patients without negative T-waves. Patients with negative T-waves extending beyond V3, seen in 20 patients, had larger low bipolar and unipolar endocardial areas, and larger epicardial low bipolar areas, compared to those with negative T-waves limited to leads V1 to V3.

ECG localization of negative T-waves regionalized to the location of substrate. Patients with downsloping elevated ST segment, all localized to leads V1, V2 had more unipolar endocardial abnormalities involving outflow in mid-right ventricle, compared to patients without downsloping elevated ST segment.

The authors concluded that in arrhythmogenic right ventricular cardiomyopathy, abnormal electric current areas were proportional to the extent of T-wave inversion on the 12 lead electrocardiogram. Marked voltage abnormalities can exist without repolarization changes. Downsloping elevated ST segment patterns in V1 and V2 occurs with more unipolar endocardial voltage abnormalities, consistent with more advanced trans neural disease.

In the next manuscript, Teresa Oloriz ...

In subgroup analyses, only patients with sudden cardiac arrest, were not associated with myocardial infarction, extracted benefit from the ICD, p < 0.001.

Further prospect of multi-center randomized control trials will be needed to confirm this observation.

After one year, 73% of the mapping group of patients were free of recurrences, compared to 50% of the control group, p = 0.03.

In the next manuscript, Teresa Oloriz ...

Previous Episode

Circulation: Arrhythmia and Electrophysiology On the Beat February 2018

Dr Wong: Welcome to the monthly podcast, "On The Beat, for Circulation: Arrhythmia, and Electrophysiology." I'm doctor Paul Wong, editor in chief, with some of the key highlights from this month's issue. We'll also here from Dr. Suraj Kapa reporting on new research from the latest journal articles in the field.

In our first article, Mathew Daly and associates examine whether a high-resolution, 9 French, infrared thermography catheter can continuously image esophageal temperatures during atrial fibrillation catheter ablation. The infrared temperature catheter was inserted nasally or orally into the esophagus, adjacent to the left atrium. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that 10 out of 16 patients experienced one or more events where the peak esophageal temperature was greater than 40 degrees centigrade. Three patients experienced temperatures greater than 50 degrees centigrade and one experienced greater than 60 degrees centigrade. Analysis of temperature data from each subject's maximal thermal event revealed high radius, 2.3 degrees centigrade per millimeter and rates of change 1.5 degrees centigrade per second, with an average length of esophageal involvement of 11.0 millimeters.

Endoscopy identified three distinct thermal lesions, all in patients with temperatures greater than 50 degrees centigrade, all resolving within two weeks. The authors concluded that infrared thermography, high-resolution mapping of esophageal temperatures during catheter ablation may be performed. Esophageal thermal injury occurs with temperatures greater than 50 degrees centigrade, and was associated with large spacial-temporal gradients.

In our next article, Nitesh Sood and associates reported on the real-world incidence and predictors of perioperative complications in transvenous lead extractions involving ICD leads in the NCDR ICD registry. Lead extraction was defined as removal of leads implanted for greater than one year. Predictors of major perioperative complication for all extraction procedures, 11,304, and for high voltage leads, 8,362, or 74% across 762 centers were analyzed, using univariate and multivariate logistic regression. Major complications occurred in 258, or 2.3% of the extraction procedures. Of these, 258 procedures with a complication, 41 or 16% required urgent cardiac surgery. Of these, 14 or 34% died during surgery. Among the total 98, or 0.9% deaths reported, 18 or 0.16% of the total occurred during extraction.

In multivariate, logistic regression analysis of all extractions, female sex, admission other than electively for the procedure, three or more leads extracted, longer implant duration, dislodgement of other leads, patients' clinical status, requiring lead extraction, such as infection or perforation, were associated with increased risk of complications. For high voltage leads, smaller lead diameter, a flat versus round coil shape, in greater proximal surface coil area, were multivariate predictors of major perioperative complications.

The rate of major complications and mortality with transvenous lead extraction is similar in the real world compared to single center studies from high volume centers. There remains a significant risk of urgent cardiac surgery with a very high mortality, and planning for appropriate cardiothoracic surgical backup is imperative.

In our next paper, Bence Hegyi and associates, have reported on the repolarization reserve in failing rabbit ventricular myocytes, and the role of calcium and beta-adrenergic effects on delayed and inward rectifier potassium currents. The authors measured the major potassium currents, IKr, IKs, IK1, and their calcium and beta-adrenergic dependence in rabbit ventricular myocytes, in chronic pressure, in volume overload, induced heart failure, and compared them to age-matched controls.

The authors made a number of observations. One, action potential duration was significantly prolonged only at lower pacing rates, 0.2 to 1 Hertz, in heart failure under physiological ionic conditions and temperature. Two, beat to beat variability of action potential duration was also significantly increased in heart failure. Three, both IKr and IKs were significantly regulated in heart failure under action potential clamp but only when cytosolic calcium was not buffered. Four, CaMKII inhibition abolished IKs upregulation in heart failure, but did not affect IKr. Five, IKs response to beta-adrenergic stimulation was also significantly diminished in heart failure, and, six, IK1 was also decreased in heart failure regardless of calcium buffering, CaMKII inhibition or beta-adrenergic stimulation.

These observations changed when cytosolic calcium was buffered. The action potential prolongation in heart failure was also significant in higher pacing rates. The authors concluded that in heart failure, calcium dependent up regulation of IKr ...

Next Episode

Circulation: Arrhythmia and Electrophysiology On the Beat April 2018

Dr. Paul Wang: Welcome to the monthly podcast On the Beat for Circulation Arrhythmia and Electrophysiology. I'm Dr Paul Wang, editor-in-chief, with some of the key highlights for this month's issue. We'll also hear from Dr. Suraj Kapa reporting on new research from the latest journal articles in the field.

In our first article, Barry Maron associates report on the long term clinical course of hypertrophic cardiomyopathy patients following ICD therapy for ventricular arrhythmias. They studied a cohort of 486 high-risk hypertrophic cardiomyopathy patients with ICDs from eight international centers. Of these 486 patients over 6.4 years, 94 patients or 19% experienced appropriate ICD interventions, terminating VT or VF. Of the 94 patients receiving appropriate ICD therapy, 87 were asymptomatic or only mildly symptomatic at the time of appropriate ICD interventions. Of these 87 patients, 74 or 85% remained in classes one or two without significant change in clinical status of the subsequent 5.9 years up to 22 years. Among the 94 patients, there was one sudden death in three patients who died from non arrhythmic hypertrophic cardiomyopathy related processes. Post ICD intervention, freedom from hypertrophic cardiomyopathy, mortality was 100% at one year, 97% at five years, and 92% at 10 years, distinctly lower than the risk of ischemic or non ischemic cardiomyopathy in ICD trials.

Hypertrophic cardiomyopathy patients with ICDs interventions reported the heightened anxiety and expectation of future shocks. However, they did not affect general psychological well-being or quality of life. The authors concluded that in hypertrophic cardiomyopathy, unlike ischemic heart disease, prevention of sudden death with ICD therapies unassociated with a significant increase in cardiovascular morbidity and mortality, nor transformation into heart failure deterioration, ICD therapy does not substantially impair overall psychological and physical well-being. In our next article, Abdulla Damluji and associates examined the cost of hospitalizations for cardiac arrest using the US nationwide inpatient sample from 2003 to 2012. Using the log transformation of inflation adjusted costs the authors examined 1,387,396 patients who were hospitalized after cardiac arrest. They had a mean age of 66 years. Inpatient procedures included coronary angiography in 15%, PCI in 7%, intra-aortic balloon pump in 4.4%, therapeutic hypothermia in 1.1%, and mechanical circulatory support in 0.1% of patients.

Notably the rates of therapeutic hypothermia increased from 0 in 2003 to 2.7 in 2012, p less than 0.001. Both hospital charges inflation adjusted costs linear increased over time. In a multi-variant analysis predictors of inflation adjusted costs included large hospitals size, urban teaching hospital, and length of stay. Among co-morbidities, atrial fibrillation or fluid and electrolytes imbalance were the most common associated with cost. The authors found that during the period between 2003 and 2012 post cardiac arrest, hospitalizations had a steady rise and associated healthcare costs likely related to increase length of stay, medical procedures and systems of care.

In our next paper, Peter Huntjens and associates examined intrinsic interventricular dyssynchrony as a predictor of human dynamic response to cardiac resynchronization. The authors use a cardiovascular computational model CircAdapt to characterize the isolated effect of intrinsic interventricular or intraventricular activation on resynchronization therapy response that is the change in LV dP/dt max. The simulated change in LV dP to dt max had a range of 1.3 to 26.5% increased considerably with increasing inter ventricular dyssynchrony. In contrast, the isolated effect of intra ventricular dyssynchrony was limited with the change in the LV dP/dt max range and the left ventricle from 12.3 to 18.3% in the right ventricle from 14 to 15.7%.

Secondly, electrocardiographic imaging derived activation characteristics of 51 CRT candidates were used to create individual models of ventricular activation in CircAdapt. The model predicted change in LV dP/dt max was close to the actual value in left bundle branch block patients with 2.7% difference between measured and simulated when only intrinsic interventricular dyssynchrony was personalized. Among non left bundle branch block patients a change in LV dP/dt max was systematically over predicted by CircAdapt with a 9.2% difference between measured and simulated. Adding intra ventricular activation to the model did not improve the accuracy of response prediction. The authors found that computer revealed intrinsic interventricular dyssynchrony is the dominant component of the electrical substrate driving the response to CRT.

In the next paper Kenji Kuroki and associates examined the use of voltage limit adjustment of substrate mapping and fast Fourier transform analysis of local ventricular bipola...