Pacemaker-mediated reentrant arrhythmia facilitated by an atrial-tracking leadless pacemaker.

INTRODUCTION: Pacemaker-mediated tachycardia is a known arrhythmia in patients with dual chamber pacemakers and defibrillators and intact ventriculoatrial (VA) conduction. We report a case of pacemaker-mediated reentrant arrhythmia (PMRA) in a patient with an atrioventricular (AV) synchronous leadless pacemaker. METHODS AND RESULTS: A 91-year-old female presented with 2:1 AV conduction and received an AV synchronous leadless pacemaker. She had atrial mechanical sense-ventricular paced beats between heart rates of 80-100 bpm more than 80% of the time. She was found to have a new cardiomyopathy and was referred for placement of biventricular pacemaker. At the time of device implantation, her electrocardiogram showed ventricular pacing with a short RP interval and superiorly directed P waves. Changes in the ventricular pacing rate resulted in changes in the atrial rate. Following device placement, her heart rate decreased to the lower rate limit of her pacemaker. The atrial mechanical sense impulse most likely was generated by a retrograde conducted P wave resulting in near incessant PMRA. CONCLUSION: PMRA may occur in patients who receive an AV synchronous leadless pacemaker with intact VA conduction and sinoatrial node dysfunction. Due to the lower rates of PMRA, this arrhythmia may be underrecognized. Interventions for and implications of PMRA need further investigation.

Evaluation of an adaptive, rule-based dosing algorithm to maintain therapeutic anticoagulation during atrial fibrillation ablation.

Background: Cerebral thromboembolism during atrial fibrillation (AF) ablation is an infrequent (0.17%) complication in part owing to strict adherence to intraprocedural anticoagulation. Failure to maintain therapeutic anticoagulation can lead to an increase in events, including silent cerebral ischemia. Objective: To evaluate a computerized, clinical decision support system (CDSS) to dose intraprocedural anticoagulation and determine if it leads to improved intraprocedural anticoagulation outcomes during AF ablation. Methods: The Digital Intern dosing algorithm is an adaptive, rule-based CDSS for heparin dosing. The initial dose is calculated from the patient's weight, baseline activated clotting time (ACT), and outpatient anticoagulant. Subsequent recommendations adapt based on individual patient ACT changes. Outcomes from 50 cases prior to algorithm introduction were compared to 139 cases using the algorithm. Results: Procedures using the dosing algorithm reached goal ACT (over 300 seconds) faster (17.6 ± 11.1 minutes vs 33.3 ± 23.6 minutes pre-algorithm, P < .001). ACTs fell below goal while in the LA (odds ratio 0.20 [0.10-0.39], P < .001) and rose above 400 seconds less frequently (odds ratio 0.21 [0.07-0.59], P = .003). System Usability Scale scores were excellent (96 ± 5, n = 7, score >80.3 excellent). Preprocedure anticoagulant, weight, baseline ACT, age, sex, and renal function were potential predictors of heparin dose to achieve ACT >300 seconds and final infusion rate. Conclusion: A heparin dosing CDSS based on rules and adaptation to individual patient response improved maintenance of therapeutic ACT during AF ablation and was rated highly by nurses for usability.

Device and non-device-guided slow breathing to reduce blood pressure: A systematic review and meta-analysis.

OBJECTIVES: Interest is increasing in nonpharmacological interventions to treat blood pressure in hypertensive and prehypertensive patients at low cardiac risk. This meta-analysis of randomized controlled trials assesses the impact of device-guided and non-device-guided (pranayama) slow breathing on blood pressure reduction in these patient populations. METHODS: We searched PubMed, EMBASE, CINAHL, Cochrane CENTRAL, Cochrane Database of Systematic Reviews, Web of Science, BIOSIS (Biological Abstracts) Citation Index and Alt HealthWatch for studies meeting these inclusion criteria: randomized controlled trial or first phase of a randomized cross-over study; subjects with hypertension, prehypertension or on antihypertensive medication; intervention consisting of slow breathing at ≤10 breaths/minute for ≥5 min on ≥3 days/week; total intervention duration of ≥4 weeks; follow-up for ≥4 weeks; and a control group. Data were extracted by two authors independently, the Cochrane Risk of Bias Tool assessed bias risk, and data were pooled using the DerSimonian and Laird random effects model. Main outcomes included changes in systolic (SBP) and/or diastolic blood pressure (DBP), heart rate (HR), and/or decreased antihypertensive medication. RESULTS: Of 103 citations eligible for full-text review, 17 studies were included in the meta-analysis. Overall, slow breathing decreased SBP by -5.62 mmHg [-7.86, -3.38] and DBP by -2.97 mmHg [-4.28, -1.66]. Heterogeneity was high for all analyses. CONCLUSIONS: Slow breathing showed a modest reduction in blood pressure. It may be a reasonable first treatment for low-risk hypertensive and prehypertensive patients who are reluctant to start medication.

Usefulness of Focused Screening Echocardiography for Collegiate Athletes.

Sudden cardiac death in a young healthy athlete is a rare but catastrophic event. The American Heart Association preparticipation screening guidelines recommend a focused history and physical without routine imaging or electrocardiogram screening. We hypothesized that a focused echocardiogram can identify structural abnormalities that may lead to sudden cardiac death in athletes, which might otherwise go undetected by history and physical. We retrospectively reviewed the charts of all incoming collegiate athletes at a single university from 2005 to 2013, all of whom had undergone a focused, 5-minute echocardiogram along with a guideline-based preparticipation history and physical (PPS H&P). Abnormal findings prompted further testing or referral. We report the prevalence of abnormal findings and the relation between an abnormal PPS H&P and screening echocardiogram. A total of 2,898 athletes were screened and 159 (5%) had findings. Forty athletes underwent further testing and evaluation. Of these athletes, 3 had newly diagnosed abnormalities that warranted restriction of participation: 1 apical-variant hypertrophic cardiomyopathy, 1 large bidirectional atrial septal defect with right ventricular dysfunction, and 1 dilated ascending aorta. Two of these athletes had a normal PPS H&P. Conversely, of the 661 athletes with an abnormal PPS H&P, only 1 (0.15%) had an abnormal screening echocardiogram. In conclusion, although the overall number was low, the 5-minute screening echocardiogram detected athletes at risk for sudden cardiac death not discovered on PPS H&P.