Circulation: Arrhythmia and Electrophysiology July 2018 Issue

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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 from this month's issue.

In our first paper, Moo-Nyun Jin, Tae-Hoon Kim, and associates examined the 1-year serial changes in cognitive function, with or without atrial fibrillation catheter ablation. They used the Montreal cognitive assessment score in 308 patients undergoing atrial fibrillation ablation, the ablation group and 50 atrial fibrillation patients on medical therapy who met the same indication for atrial fibrillation ablation, the control group at baseline three months and 12 months. Cognitive impairment was defined as a published cutoff score of less than 23 points. Pre-ablation cognitive impairment was a detected in 18.5%. The Montreal cognitive assessment score significantly improved one year after radio frequency ablation. In both the overall ablation group, 24.9 to 26.4 p less than 0.001, and the propensity matched ablation group 25.4 to 26.5, but not in the control group. 25.4 to 24.8 p equals 0.012. Pre-ablation cognitive pyramid odds ratio 13.7, was independently associated with an improvement in one-year post ablation cognitive function.

In our next paper, Zian Tseng, James Salazar and associates studied World Health Organization defined sudden cardiac deaths autopsied in the POstmortem Systemic InvesTigation of sudden cardiac death, the POST SCD study to determine whether premortem characteristics could identify autopsy defined sudden arrhythmic death among presumed sudden cardiac deaths. They prospectively identified 615 World Health Organization defined sudden cardiac deaths, of which 144 were witnessed. Autopsy defined sudden arrhythmic death had no extra cardiac or acute heart failure cause of death. Of the 615 presumed sudden critic deaths, 348 or 57% were autopsy defined, sudden arrhythmic deaths. For witness cases, using an emergency medical system model area under the receiver operator curve 0.75, included presenting rhythm of ventricular tech or cardiac fibrillation, pulseless electrical activity, while the comprehensive model, adding medical record data and depression, area under the curve 0.78. If only VTVF witness cases, 48 of those were classified as sudden arrhythmic death. The sensitivity was 0.46, and specificity 0.90.

For unwitnessed cases, the emergency medical system model, area under the curve 0.68, included black race, male sex, age, time since last seen normal, while the comprehensive, area into the curve 0.75, added the use of beta blockers, antidepressants, QT prolonging drugs, opiates, illicit drugs and dyslipidemia. If only unwitnessed cases, less than one hour, n equals 59, were classified as sudden arrhythmic deaths, the sensitivities were 0.18, and specificity was 0.95. The authors concluded that models could identify pre-mortem characteristics to better specify autopsy defined sudden arrhythmic deaths, among presumed sudden cardiac arrests. The authors suggest that the World Health Organization definition can be improved by restricting witnessed sudden cardiac deaths to ventricular tachycardia fibrillation or non-pulseless electrical activity rhythms in unwitnessed cases to less than one hour since last normal, at a cost of sensitivity.

In our next paper, Rafael Jaimes III and associates performed optical mapping of trends, membrane, voltage and pacing studies on isolated Langendorff-perfused rat hearts to assess the cardiac electrophysiology after mono-2-ethylhexyl phthalate, a phthalate with documented exposure in intensive care patients. The authors found that a 30-minute exposure to mono-2-ethylhexyl phthalate increased the atrioventricular node effector in period 147 milliseconds compared to 170 milliseconds in controls and increased the ventricular effective refractory periods of 117 milliseconds compared to 77.5 milliseconds in controls. Optical mapping revealed prolonged action potential duration at slower pacing cycle lengths. Mono-2-ethylhexyl phthalate exposure also slowed epicardial conduction velocity, 25 centimeters per second compared to 60 centimeters per second in controls. The authors concluded that acute mono-2-ethylhexyl phthalate exposure, at clinically relevant doses, has a significant effect on cardiac electrophysiology in the intact heart. Heightened clinical exposure to plasticized medical products may have cardiac safety implications and lead to cardiac arrhythmias.

In our next paper, Stephan Willems and associates report the use of a novel, non-contact imaging and mapping system that uses ultrasound to reconstruct atrial chamber anatomy and measure timing and density of dipolar, ionic activation or charge density across the myocardium to guide ablation of atrial arrhythmias. They conducted a prospective non-randomized study, the UNCOVER AF trial which was conducted at 13 centers across Europe and Canada. In 127 patients with persistent atrial fibrillation who underwent mapping and catheter ablation, acute procedural efficacy of 98% was seen. At 12 months, the single procedure freedom from atrial fibrillation, on or off antiarrhythmic drugs, was 72.5%, with 23% undergoing retreatments following one or two procedures. Freedom from atrial fibrillation was 93.2%. The primary safety outcome was 98% was no device related major adverse events reported.

In our next paper, Anne-Floor Quast, Niek Beurskens, and associates describe a novel, completely extracardiac pacing system, with a lead in the anterior mediastinum, outside the pericardium and circulatory system. A total of 166 or 95% out of 174 patients had a viable lead access path through the fourth, fifth, or sixth intercostal space. Access to the targeted implant location using delivery tool was successful in all five cadavers and three humans, without use of fluoroscopy, with an average lead delivery time of 121 seconds. No damage to the lung, pericardium, heart or internal thoracic vessels occurred. Pacing performance in six human subjects showed a voltage threshold of 4.7 volts in a threshold pulse width of 1.8 milliseconds.

In our next paper, Yasuhiro Shirai and associates compare the ability to identify ventricular tachycardia isthmuses in ischemic and nonischemic cardiomyopathies. Of 445 patients, 228 with ischemic cardiomyopathy and 217 with nonischemic cardiomyopathy, undergoing VT ablation. Detailed entrainment mapping of at least one tolerated VT was performed in 111 patients, 71 with ischemic cardiomyopathy and 40 with nonischemic cardiomyopathy. Of 89 nonischemic cardiomyopathy VTs, the isthmus could be identified by endocardial entrainment in 55 or 62%, compared to only eight out of 47 or 17% nonischemic cardiomyopathy VTs, p less than 0.01. With combined endocardial and epicardial mapping, the isthmus could be identified in 56 or 63% ischemic cardiomyopathy VTs, and 12 or 26% of nonischemic cardiomyopathy VTs, p less than 0.01, while a similar proportion of patients any critical component, defined as entrance, isthmus or exit, could be identified in 85% of ischemic cardiomyopathy VTs and 79% of nonischemic cardiomyopathy VTs, p equals 0.3. Complete success, no inducible VT at the end of the procedure was 82% versus 65%, p equals 0.04 and a one-year single procedure VT survival, 82% versus 55%, p less than 0.01. Both higher in patients with ischemic cardiomyopathy. The authors concluded that among mappable ischemic cardiomyopathy VTs, critical circuit components can be usually identified on the endocardium. In contrast, among mappable nonischemic cardiomyopathy VTs, although some critical components can be typically identified with the addition of epicardial mapping, the isthmus is less commonly identified, possibly due to midmyocardial location.

In our next paper, Miki Yokokawa and associates targeted documented but non-inducible clinical VTs, based on stored, implantable cardioverter defibrillator electrograms. Radio frequency ablation was performed in a consecutive group of 66 postinfarction VTs, in whom clinical VTs were non-inducible during an ablation procedure. In the first 33 patients, the control group, only inducible VTs were targeted. In the second 33 patients, non-inducible clinical VTs were targeted by pace mapping based on stored ICD-electrograms, the ICD electrogram guided ablation group. VT recurred in five patients or 15% in the ICD-electrogram guided approach, and in 13% or 39% in the control group. Freedom from recurrent VT was higher, p equals 0.04, in the ICD-electrogram-guided group, but there was no difference in ventricular fibrillation or total mortality between groups.

In our next paper, Albert Feeny and associates examined whether machine learning could predict cardiac resynchronization therapy or CRT response. A training cohort was created from all Johns Hopkins patients and an equal number of randomly sampled Cleveland Clinic patients. All remaining patients comprise the testing cohort. Response was defined as greater than or equal to 10% increase in left ventricular ejection fraction. Machine learning models were developed to predict CRT response using different combinations of classification algorithms in clinical variable sets on the training cohort. 925 patients were included. On the training cohort, the best machine learning model was a naive Bayes classifier using nine variables, QRS morphology, QRS duration, New York Heart Association classification, left ventricular ejection fraction and end-diastolic diameter, sex, ischemic cardiomyopathy, atrial fibrillation, and epicardial LV lead. On the testing cohort, machine learning demonstrated better response prediction than guidelines, area under the curves 0.7 versus 0.65, p equals 0.012, and greater discrimination of event-free survival, concordance index 0.61 versus 0.56, p less than 0.001. The fourth quartile of machine learning model had greatest risk of reaching the composite endpoint, while the first quartile had the least, hazard ratio of 0.34, p less than 0.001. The authors found that machine learning with nine variables incrementally improved prediction of CRT response and survival beyond guidelines, but its performance with not improved by incorporating more variables.

In our next paper, Bernhard Kaess, Charlotte Andersson and associates examine the familial clustering of cardiac conduction defects in the Framingham heart study, using multivariable-adjusted logistic regression models to investigate the association of parental AV block, complete bundle branch block, or a pacemaker insertion with occurrence of cardiac conduction abnormalities on offspring. Individuals with at least one effected parent with a conduction defect had at 1.65-fold odds for manifesting AV block, and 1.62-fold odds for developing complete bundle branch block. If at least one parent had any electrocardiographic conduction defect or pacemaker insertion, the offspring had 1.62-fold odds for experiencing any of these conditions. The Danish and nationwide administrative registries of nearly 3 million individuals and about five thousand incident pacemaker implantations, individuals with at least one first degree relative with a history of pacemaker insertion, had a multivariable-adjusted 1.68-fold incident rate ratio of undergoing pacemaker insertion. If the affected relative was less than or equal to 45 years of age, the incident rate ratio was markedly increased to 51.0.

In our final paper, a review article, Venkat Nagarajan, Siew Ho Yen, and Sabine Ernst provide a detailed discussion of anatomic landmarks and considerations that will aid in his bundle pacing lead implantation.

That's it for this month. We hope that you'll find the journal to be the go to place for everyone interested in the field. See you next time.

This program is copyright American Heart Association 2019.

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