Infections Associated with Resterilized Pacemakers and Defibrillators.

BACKGROUND: Access to pacemakers and defibrillators is problematic in places with limited resources. Resterilization and reuse of implantable cardiac devices obtained post mortem from patients in wealthier nations have been undertaken, but uncertainty around the risk of infection is a concern. METHODS: A multinational program was initiated in 1983 to provide tested and resterilized pacemakers and defibrillators to underserved nations; a prospective registry was established in 2003. Patients who received reused devices in this program were matched in a 1:3 ratio with control patients who received new devices implanted in Canada. The primary outcome was infection or device-related death, with mortality from other causes modeled as a competing risk. RESULTS: Resterilized devices were implanted in 1051 patients (mean [±SD] age, 63.2±18.5 years; 43.6% women) in Mexico (36.0%), the Dominican Republic (28.1%), Guatemala (26.6%), and Honduras (9.3%). Overall, 85% received pacemakers and 15% received defibrillators, with one (55.5%), two (38.8%), or three (5.7%) leads. Baseline characteristics did not differ between these patients and the 3153 matched control patients. At 2 years of follow-up, infections had occurred in 21 patients (2.0%) with reused devices and in 38 (1.2%) with new devices (hazard ratio, 1.66; 95% confidence interval, 0.97 to 2.83; P = 0.06); there were no device-related deaths. The most common implicated pathogens were Staphylococcus aureus and S. epidermidis. CONCLUSIONS: Among patients in underserved countries who received a resterilized and reused pacemaker or defibrillator, the incidence of infection or device-related death at 2 years was 2.0%, an incidence that did not differ significantly from that seen among matched control patients with new devices in Canada.

Importance of genetic testing in unexplained cardiac arrest.

AIMS: Genetic testing is recommended in specific inherited heart diseases but its role remains unclear and it is not currently recommended in unexplained cardiac arrest (UCA). We sought to assess the yield and clinical utility of genetic testing in UCA using whole-exome sequencing (WES). METHODS AND RESULTS: Survivors of UCA requiring external defibrillation were included from the Cardiac Arrest Survivor with Preserved Ejection fraction Registry. Whole-exome sequencing was performed, followed by assessment of rare variants in previously reported cardiovascular disease genes. A total of 228 UCA survivors (mean age at arrest 39 ± 13 years) were included. The majority were males (66%) and of European ancestry (81%). Following advanced clinical testing at baseline, the likely aetiology of cardiac arrest was determined in 21/228 (9%) cases. Whole-exome sequencing identified a pathogenic or likely pathogenic (P/LP) variant in 23/228 (10%) of UCA survivors overall, increasing the proportion of 'explained' cases from 9% only following phenotyping to 18% when combining phenotyping with WES. Notably, 13 (57%) of the 23 P/LP variants identified were located in genes associated with cardiomyopathy, in the absence of a diagnosis of cardiomyopathy at the time of arrest. CONCLUSIONS: Genetic testing identifies a disease-causing variant in 10% of apparent UCA survivors. The majority of disease-causing variants was located in cardiomyopathy-associated genes, highlighting the arrhythmogenic potential of such variants in the absence of an overt cardiomyopathy diagnosis. The present study supports the use of genetic testing including assessment of arrhythmia and cardiomyopathy genes in survivors of UCA.

Reducing radiation exposure during procedures performed in the electrophysiology laboratory.

INTRODUCTION: Expert societies recently published strong recommendations to reduce the exposure of patients and staff to ionizing radiation (IR) during interventional and electrophysiology (EP) procedures. However, adherence to these guidelines remains difficult and the impact of implementing such recommendations is poorly characterized. METHODS AND RESULTS: We conducted a single-center cohort study to quantify radiation exposure over time in three EP laboratories at the Montreal Heart Institute during 5,546 consecutive procedures from 2012 to 2015 by 11 primary operators. Overall, 2,618 (47.2%) procedures were catheter-based and 2,928 (52.8%) were device interventions. Interventions to reduce radiation exposure included educational initiatives to raise awareness (i.e., limiting cine acquisition, patient position, table height), slower frame rate, lower radiation dose per pulse, collimation, and integration with 3-D mapping systems and/or MediGuide technology. An 85% reduction in IR exposure was observed from 2012 to 2015, with the mean dose-area-product (DAP) decreasing from 7.65 ± 0.05 Gy·cm2 to 1.15 ± 0.04 Gy·cm2 (P < 0.001). This was true for catheter-based procedures (mean DAP 16.99 ± 0.08 to 2.00 ± 0.06 Gy·cm2 , P < 0.001) and device interventions (mean DAP 4.18 ± 0.06 to 0.64 ± 0.05 Gy·cm2 , P < 0.001). The median effective dose of IR recorded per quarter by 282 cervical dosimeters on EP staff decreased from 0.57 (IQR 0.18, 1.03) mSv in 2012 to 0.00 (IQR 0.00, 0.19) mSv in 2015, P < 0.001. CONCLUSION: Enforcing good clinical practices with simple measures and low-dose fluoroscopy settings are highly effective in reducing IR exposure in the EP lab. These promising results should encourage other EP labs to adopt similar protective measures.

Focal Transcatheter Cryoablation: Is a Four-Minute Application Still Required?

INTRODUCTION: The standard 4-minute application time for transcatheter cryoablation was determined in the 1990s when the system employed less potent chlorofluorocarbon refrigerants. The current refrigerant, nitrous oxide, generates substantially colder temperatures, with a faster cooling rate. METHODS AND RESULTS: We conducted a preclinical study on 32 mongrel dogs with stratified randomization of right atrial, right ventricular, and left ventricular chambers to 2-minute versus 4-minute application times using 8-mm electrode tip cryocatheters (Freezor Max, Medtronic CryoCath LP, Montreal, Canada). Animals were sacrificed one month after the procedure. Three-dimensional morphometric analyses were conducted in a blinded fashion. A total of 193 identified ablation lesions were processed for histological analyses, 102 with 2-minute applications and 91 with 4-minute applications. Ablation lesion surface area (167.8 ± 21.6 mm2 vs. 194.3 ± 22.6 mm2 , P = 0.40), maximum depth (4.4 ± 0.2 mm vs. 4.5 ± 0.2 mm, P = 0.71), and volume (125.7 ± 69.5 mm3 vs. 141.0 ± 83.5 mm3 , P = 0.25) were similar between groups. Overall, 90.2% of ablation lesions in the right atrium were transmural, 45.6% in the right ventricle, and 2.4% in the left ventricle, with no differences between 2-minute and 4-minute application times (P = 0.55). Thrombus was detected on the endocardial surface of 0.0% and 3.3% of ablation lesions created with 2-minute and 4-minute application times, respectively (P = 0.10). CONCLUSION: Single 2-minute and 4-minute application times result in catheter ablation lesions of similar size using the modern cryoablation system with nitrous oxide as a refrigerant. While these findings suggest the potential to reduce the standard 4-minute application time, further studies are required to compare clinical efficacy.

Subclavian access using a three-dimensional electromagnetic cardiovascular navigation system: novel approach to access the venous system during device implant procedures.

We report a case in which a novel three-dimensional (3D) electromagnetic cardiovascular navigation system (MediGude™, St. Jude Medical, St. Paul, MN, USA) was used to create a 3D reconstruction of the axillary vein and its anatomic course to guide its successful puncture and cannulation. The MediGuide system's projection accuracy has proved to offer a level of precision that is sufficient to achieve axillary vein access. This highlights its enormous possibilities to obtain 3D venous system reconstruction with minimal fluoroscopic use when performing cardiac or even non-cardiac procedures.

Contact-force-guided vs. contact-force-blinded catheter ablation of typical atrial flutter: a prospective study.

AIMS: It remains unknown whether contact force (CF) sensing technology is of value for cavotricuspid isthmus (CTI) ablation. We prospectively evaluated procedural parameters and outcomes of CF-guided vs. CF-blinded CTI ablation for typical atrial flutter (AFL). METHODS AND RESULTS: A total of 70 consecutive patients (62.5 ± 10.9 years) undergoing CTI ablation for AFL were prospectively enrolled, 35 in CF-blinded and 35 in CF-guided groups. A CF-sensing catheter (power 25-35 W) was used in all. In the CF-guided group, CF target range was 10-25 g, whereas in the CF-blinded group, the operator was blinded to CF. The isthmus was divided into anterior, middle, and posterior segments for region-specific CF analysis. The procedural endpoint of bidirectional isthmus block following a 20-min observation period was achieved in all. A trend towards lower fluoroscopy and procedure duration was observed when the CF-guided group was compared with the CF-blinded group. The total radiofrequency (RF) energy delivery time required to achieve bidirectional block was significantly lower in the CF-guided vs. CF-blinded group [10.0 min (IQR 8.3;15.1) vs. 15.9 min (IQR 9.6;24.7), P= 0.0020], with a significant inverse correlation between CF and total RF delivery time (r = -0.36; P= 0.0027). Mean CF measurements significantly increased from anterior to posterior anatomical zones of CTI in the CF-blinded group (ANOVA P= 0.0466). CONCLUSIONS: Catheter ablation of AFL guided by real-time CF assessment results in a significant reduction in total RF delivery time. Real-time CF measurements facilitate the maintenance of homogenous efficient contact all along the CTI, particularly in the anterior segment where CF is generally lower.

The dream of near-zero X-rays ablation comes true.

While radiation exposure related to natural sources plays a minor role, medicine-related exposure, represents, to date, a major exposure source. Within this exposure interventional electrophysiology is a relevant contributor. Unfortunately, no safe dose in radioprotection exists, the negative acute and long-term effects of radiological exposure may emerge at any radiation exposure dose. For this reason, patients and physicians should be aware of the risk of radiation exposure and the benefits of the imaging/procedure balanced by the required radiation exposure. Given this, performing a near to zero X-rays transcatheter ablation procedure should therefore represent an aim for all electrophysiological lab. Fortunately, the introduction of electroanatomic mapping systems, have provided the possibility to perform simple and complex electrophysiological procedures avoiding, or at least, limiting the use of radiations. The present review summarizes state of the art of feasibility and safety of the near to zero approach for the main electrophysiological procedures, highlighting the potential health benefits.

Adenosine-guided pulmonary vein isolation for the treatment of paroxysmal atrial fibrillation: an international, multicentre, randomised superiority trial.

BACKGROUND: Catheter ablation is increasingly used to manage atrial fibrillation, but arrhythmia recurrences are common. Adenosine might identify pulmonary veins at risk of reconnection by unmasking dormant conduction, and thereby guide additional ablation to improve arrhythmia-free survival. We assessed whether adenosine-guided pulmonary vein isolation could prevent arrhythmia recurrence in patients undergoing radiofrequency catheter ablation for paroxysmal atrial fibrillation. METHODS: We did this randomised trial at 18 hospitals in Australia, Europe, and North America. We enrolled patients aged older than 18 years who had had at least three symptomatic atrial fibrillation episodes in the past 6 months, and for whom treatment with an antiarrhythmic drug failed. After pulmonary vein isolation, intravenous adenosine was administered. If dormant conduction was present, patients were randomly assigned (1:1) to additional adenosine-guided ablation to abolish dormant conduction or to no further ablation. If no dormant conduction was revealed, randomly selected patients were included in a registry. Patients were masked to treatment allocation and outcomes were assessed by a masked adjudicating committee. Patients were followed up for 1 year. The primary outcome was time to symptomatic atrial tachyarrhythmia after a single procedure in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT01058980. FINDINGS: Adenosine unmasked dormant pulmonary vein conduction in 284 (53%) of 534 patients. 102 (69·4%) of 147 patients with additional adenosine-guided ablation were free from symptomatic atrial tachyarrhythmia compared with 58 (42·3%) of 137 patients with no further ablation, corresponding to an absolute risk reduction of 27·1% (95% CI 15·9-38·2; p<0·0001) and a hazard ratio of 0·44 (95% CI 0·31-0·64; p<0·0001). Of 115 patients without dormant pulmonary vein conduction, 64 (55·7%) remained free from symptomatic atrial tachyarrhythmia (p=0·0191 vs dormant conduction with no further ablation). Occurrences of serious adverse events were similar in each group. One death (massive stroke) was deemed probably related to ablation in a patient included in the registry. INTERPRETATION: Adenosine testing to identify and target dormant pulmonary vein conduction during catheter ablation of atrial fibrillation is a safe and highly effective strategy to improve arrhythmia-free survival in patients with paroxysmal atrial fibrillation. This approach should be considered for incorporation into routine clinical practice. FUNDING: Canadian Institutes of Health Research, St Jude Medical, Biosense-Webster, and M Lachapelle (Montreal Heart Institute Foundation).

Reducing Radiation Exposure During CRT Implant Procedures: Single-Center Experience With Low-Dose Fluoroscopy Settings and a Sensor-Based Navigation System (MediGuide).

INTRODUCTION: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in substantial ionizing radiation (IR) exposure to the patient and operator. We assessed the impact of lower-dose fluoroscopy settings and a sensor-based electromagnetic tracking system (MediGuide™, MDG) on reducing IR exposure during CRT implantation. METHODS: A single-center 2-group cohort study was conducted on 348 consecutive patients, age 66.4 ± 11.0 years, 80.4% male, with CRT implant procedures from 2013 to 2015. Patients were arbitrarily assigned to MDG (N = 239) versus no MDG (N = 109) guidance. Lower-dose fluoroscopy settings were adopted in January 2015 (3 instead of 6 fps; 23 instead of 40 nGy/pulse; N = 101). RESULTS: Overall, MDG was associated with an 82.1% reduction in IR exposure (393 µGray·m2 vs. 2191 µGray·m2 , P < 0.001). Lower-dose fluoroscopy resulted in a 59.5% reduction in IR-exposure without MDG (1055 µGray·m2 vs. 2608 µGray·m2 , P < 0.001) and 81.8% reduction with MDG (108 µGray·m2 vs. 595 µGray·m2 , P < 0.001). Low-dose fluoroscopy combined with MDG was associated with a 95.9% lower exposure to IR when compared to standard fluoroscopy without MDG (108 µGray·m2 vs. 2608 µGray·m2 , P < 0.001). Procedures with MDG were shorter (96 minutes vs. 123 minutes, P < 0.001) and associated with a trend towards a higher success rate (94.6% vs. 89.0%, P = 0.062), with fewer coronary sinus cannulation failures (2.1% vs. 6.4%, P = 0.040). CONCLUSION: Low-dose fluoroscopy settings are highly effective (>50%) in reducing IR exposure during CRT implant procedures. When combined with MDG, >95% reduction in IR exposure is achieved. Moreover, MDG shortens procedural duration and may improve acute procedural outcomes.

ECG Features Associated With Adverse Cardiovascular Outcomes in Patients With Atrial Fibrillation: A Combined AFFIRM and AF-CHF Analysis.

BACKGROUND: The association between standard parameters from a simple 12-lead ECG (i.e., QRS duration and PR, JT, and QT intervals) and adverse cardiovascular outcomes (cardiovascular mortality, all-cause mortality, arrhythmic mortality, and hospitalizations) in patients with a history of atrial fibrillation (AF) has not been previously studied. METHODS AND RESULTS: A pooled analysis of patient-level data was conducted on 5,436 patients, age 68.2 ± 8.3 years, 34.8% female, with a history of non-permanent AF randomized in AFFIRM and AF-CHF trials. The predictive value of ECG parameters was assessed in AF and sinus rhythm in multivariate Cox regression models. During a follow-up of 40.8 ± 16.3 months, QRS duration >120 milliseconds was independently associated with all-cause mortality (hazard ratio [HR] 1.46, 95% confidence interval [CI; 1.21-1.76] in AF, P < 0.001), cardiovascular mortality (HR 1.75, 95% CI (1.15-2.65) in sinus rhythm, P = 0.009; HR 1.56, 95% CI [1.27-1.93] in AF, P < 0.001), arrhythmic mortality (HR 1.90, 95% CI [1.09-3.32] in sinus, P = 0.024; HR 1.84, 95% CI [1.35-2.51] in AF, P < 0.001), any hospitalization (HR 1.15, 95% CI [1.02-1.29] in AF, P = 0.027), and cardiovascular hospitalization (HR 1.21, 95% CI [1.06-1.37] in AF; P = 0.004). Increased PR interval (>200 milliseconds) was independently associated with cardiovascular (HR 1.56, 95% CI [1.11-2.21], P = 0.010) and arrhythmic (HR 1.91, 95% CI [1.14-3.18], P = 0.004) mortality. The JT and QTc intervals were not predictive of mortality. CONCLUSIONS: Simple parameters from standard ECGs are significantly and independently associated with adverse cardiovascular outcomes in patients with a history of AF.

Treatment Failure With Rhythm and Rate Control Strategies in Patients With Atrial Fibrillation and Congestive Heart Failure: An AF-CHF Substudy.

INTRODUCTION: Rate and rhythm control strategies for atrial fibrillation (AF) are not always effective or well tolerated in patients with congestive heart failure (CHF). We assessed reasons for treatment failure, associated characteristics, and effects on survival. METHODS AND RESULTS: A total of 1,376 patients enrolled in the AF-CHF trial were followed for 37  ±  19 months, 206 (15.0%) of whom failed initial therapy leading to crossover. Rhythm control was abandoned more frequently than rate control (21.0% vs. 9.1%, P < 0.0001). Crossovers from rhythm to rate control were driven by inefficacy, whereas worsening heart failure was the most common reason to crossover from rate to rhythm control. In multivariate analyses, failure of rhythm control was associated with female sex, higher serum creatinine, functional class III or IV symptoms, lack of digoxin, and oral anticoagulation. Factors independently associated with failure of rate control were paroxysmal (vs. persistent) AF, statin therapy, and presence of an implantable cardioverter-defibrillator. Crossovers were not associated with cardiovascular mortality (hazard ratio [HR] 1.11 from rhythm to rate control; 95% confidence interval [95% CI, 0.73-1.73]; P = 0.6069; HR 1.29 from rate to rhythm control; 95% CI, 0.73-2.25; P = 0.3793) or all-cause mortality (HR 1.16 from rhythm to rate control, 95% CI [0.79-1.72], P = 0.4444; HR 1.15 from rate to rhythm control, 95% [0.69, 1.91], P = 0.5873). CONCLUSIONS: Rhythm control is abandoned more frequently than rate control in patients with AF and CHF. The most common reasons for treatment failure are inefficacy for rhythm control and worsening heart failure for rate control. Changing strategies does not impact survival.

Blood Pressure and Atrial Fibrillation: A Combined AF-CHF and AFFIRM Analysis.

BACKGROUND: Hypertension is an established risk factor for new-onset atrial fibrillation (AF). However, the relationship between blood pressure and recurrent AF is less well understood. METHODS AND RESULTS: A pooled analysis of patient-level data from AFFIRM and AF-CHF trials was conducted on all 2,715 patients with paroxysmal or persistent AF, 68 ± 8 years, 66% male, randomized to rhythm control and followed for 40.6 ± 16.5 months. We assessed the impact of a baseline systolic blood pressure (SBP; <120 mmHg [N = 1,008], 120-140 mmHg [N = 930], >140 mmHg [N = 777]) on recurrent AF and proportion of time spent in AF. In patients with LVEF >40% (N = 1,719), SBP was not associated with recurrent AF in multivariate regression analyses (P = 0.752). In contrast, in patients with LVEF ≤40% (N = 996), the AF recurrence rate was higher in those with an SBP >140 mmHg compared to 120-140 mmHg (hazard ratio 1.47; 95% CI [1.12-1.93], P = 0.005). The rate of recurrent AF was similar in patients with SBP <120 mmHg compared to 120-140 mmHg (hazard ratio 1.15; 95% CI [0.92-1.43], P = 0.225). Consistently, the proportion of time spent in AF was not influenced by SBP in patients with LVEF >40% (P = 0.645). However, in patients with LVEF ≤40%, the adjusted mean proportion of time spent in AF was 17.2% if SBP was <120 mmHg, 15.4% for SBP 120-140 mmHg, and 24.0% for SBP >140 mmHg (P = 0.025). CONCLUSION: Systolic blood pressure is an important determinant of recurrent AF and overall AF burden in patients with left ventricular dysfunction (LVEF≤40%) but not in those with preserved ventricular function.

Reducing radiation exposure during CRT implant procedures: early experience with a sensor-based navigation system.

BACKGROUND: Cardiac resynchronization therapy (CRT) implant procedures are often complex and prolonged, resulting in significant ionizing radiation (IR) exposure to the patient and operator. We report our early experience working with a novel sensor-based electromagnetic tracking system (MediGuide™, MDG, St. Jude Medical Inc., St. Paul, MN, USA), in terms of procedural IR exposure reduction. METHODS AND RESULTS: Information regarding patient demographics, procedural details, procedural duration, and IR exposure were prospectively collected on 130 consecutive CRT procedures performed between January 2013 and January 2014. Sixty procedures were performed with MDG guidance, and 70 were performed without MDG guidance. Despite a nonsignificant trend toward shorter procedure duration with the use of MDG (120 minutes vs 138 minutes with non-MDG, P = 0.088), a 66% reduction in total IR exposure (median 769 µGray · m(2) vs 2,608 µGray · m(2), P < 0.001) was found. This reduction was primarily driven by a >90% reduction in IR dose required to cannulate the coronary sinus (median 80 µGray · m(2) vs 922 µGray · m(2), P < 0.001), and to a lesser extent from a reduction in IR dose required for LV lead placement (median 330 µGray·m(2) vs 737 µGray · m(2), P = 0.059). In addition, a significant learning curve effect was observed with a significantly shorter procedural duration for the last 15 cases compared to the first 15 cases (median 98 minutes vs 175 minutes, P < 0.001). CONCLUSION: The nonfluoroscopic MDG positioning system is associated with a dramatic reduction in exposure to IR during CRT implant procedures, with a 90% decrease in the IR dose required to cannulate the coronary sinus. A steep learning curve was quantified.

Cardiac resynchronization therapy in patients with heart failure and a QRS complex <120 milliseconds: the Evaluation of Resynchronization Therapy for Heart Failure (LESSER-EARTH) trial.

BACKGROUND: Although the benefits of cardiac resynchronization therapy are well established in selected patients with heart failure and a prolonged QRS duration, salutary effects in patients with narrow QRS complexes remain to be demonstrated. METHODS AND RESULTS: The Evaluation of Resynchronization Therapy for Heart Failure (LESSER-EARTH) trial is a randomized, double-blind, 12-center study that was designed to compare the effects of active and inactive cardiac resynchronization therapy in patients with severe left ventricular dysfunction and a QRS duration <120 milliseconds. The trial was interrupted prematurely by the Data Safety and Monitoring Board because of futility and safety concerns after 85 patients were randomized. Changes in exercise duration after 12 months were no different in patients with and without active cardiac resynchronization therapy (-0.7 minutes [95% confidence interval (CI), -2.9 to 1.5] versus 0.8 minutes [95% CI, -1.2 to 2.9]; P=0.31]. Similarly, no significant differences were observed in left ventricular end-systolic volumes (-6.4 mL [95% CI, -18.8 to 5.9] versus 3.1 mL [95% CI, -9.2 to 15.5]; P=0.28) and ejection fraction (3.3% [95% CI, 0.7-6.0] versus 2.1% [95% CI, -0.5 to 4.8]; P=0.52). Moreover, cardiac resynchronization therapy was associated with a significant reduction in the 6-minute walk distance (-11.3 m [95% CI, -31.7 to 9.7] versus 25.3 m [95% CI, 6.1-44.5]; P=0.01), an increase in QRS duration (40.2 milliseconds [95% CI, 34.2-46.2] versus 3.4 milliseconds [95% CI, 0.6-6.2]; P<0.0001), and a nonsignificant trend toward an increase in heart failure-related hospitalizations (15 hospitalizations in 5 patients versus 4 hospitalizations in 4 patients). CONCLUSIONS: In patients with a left ventricular ejection fraction ≤35%, symptoms of heart failure, and a QRS duration <120 milliseconds, cardiac resynchronization therapy did not improve clinical outcomes or left ventricular remodeling and was associated with potential harm. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00900549.

Histopathology of cryoballoon ablation-induced phrenic nerve injury.

INTRODUCTION: Hemi-diaphragmatic paralysis is the most common complication associated with cryoballoon ablation for atrial fibrillation, yet the histopathology of phrenic nerve injury has not been well described. METHODS AND RESULTS: A preclinical randomized study was conducted to characterize the histopathology of phrenic nerve injury induced by cryoballoon ablation and assess the potential for electromyographic (EMG) monitoring to limit phrenic nerve damage. Thirty-two dogs underwent cryoballoon ablation of the right superior pulmonary vein with the objective of inducing phrenic nerve injury. Animals were randomized 1:1 to standard monitoring (i.e., interruption of ablation upon reduction in diaphragmatic motion) versus EMG guidance (i.e., cessation of ablation upon a 30% reduction in the diaphragmatic compound motor action potential [CMAP] amplitude). The acute procedural endpoint was achieved in all dogs. Phrenic nerve injury was characterized by Wallerian degeneration, with subperineural injury to large myelinated axons and evidence of axonal regeneration. The degree of phrenic nerve injury paralleled the reduction in CMAP amplitude (P = 0.007). Animals randomized to EMG guidance had a lower incidence of acute hemi-diaphragmatic paralysis (50% vs 100%; P = 0.001), persistent paralysis at 30 days (21% vs 75%; multivariate odds ratio 0.12, 95% confidence interval [0.02, 0.69], P = 0.017), and a lesser severity of histologic injury (P = 0.001). Mature pulmonary vein ablation lesion characteristics, including circumferentiality and transmurality, were similar in both groups. CONCLUSION: Phrenic nerve injury induced by cryoballoon ablation is axonal in nature and characterized by Wallerian degeneration, with potential for recovery. An EMG-guided approach is superior to standard monitoring in limiting phrenic nerve damage.

Efficacy of amiodarone in patients with atrial fibrillation with and without left ventricular dysfunction: a pooled analysis of AFFIRM and AF-CHF trials.

INTRODUCTION: Despite amiodarone's established safety profile in the setting of heart failure, it is unknown whether its impact on cardiovascular outcomes in patients with atrial fibrillation is modulated by left ventricular function. METHODS AND RESULTS: A pooled analysis of 3,307 patients (age 68.0 ± 0.2 years; 31.1% female) enrolled in AFFIRM and AF-CHF trials was conducted to assess the effect of rhythm control with amiodarone on cardiovascular outcomes, according to left ventricular systolic function. In amiodarone-treated patients (N = 1,107), freedom from recurrent atrial fibrillation was 84% and 45% at 1 and 5 years, respectively, with no differences according to left ventricular function (P = 0.8754). Similarly, the adjusted proportion of time spent in atrial fibrillation (15.0 ± 1.8%) did not vary according to ventricular function (P = 0.6094). Over 40.0 ± 0.3 months of follow-up, 1,963 (59.4%) patients required at least one hospitalization, 1,401 (42.6%) of whom had cardiovascular-related hospitalizations. Adjusted all-cause and cardiovascular hospitalization rates were similar with amiodarone versus rate control in all patients and in subgroups with and without severe left ventricular dysfunction. A total of 729 (22.0%) patients died, 498 (15.1%) from cardiovascular causes. Adjusted all-cause and cardiovascular mortality rates were similar with amiodarone versus rate control overall and in subgroups with and without severe left ventricular dysfunction. CONCLUSION: Amiodarone's efficacy in maintaining sinus rhythm and reducing the burden of atrial fibrillation is similar in the presence or absence of severe left ventricular dysfunction. Rhythm control with amiodarone is associated with comparable hospitalization and mortality rates to rate control in patients with and without left ventricular dysfunction.

Design of an acute dP/dt hemodynamic measurement protocol to isolate cardiac effect of pacing.

BACKGROUND: Invasively measured maximum increase in left ventricular pressure (LV dP/dtmax) has been used to assess biventricular (BiV) pacing. We quantified extracardiac factors contributing to its variability, and developed a protocol to minimize these effects in an acute pacing experiment. METHODS AND RESULTS: Continuous pressure was recorded by a guidewire sensor placed in the LV. Four to six test pacing interventions were performed, each repeated 3 times and followed by a baseline pacing configuration. Maximum increase in LV dP/dtmax from any measurement of BiV pacing was median 20.3% in 25 patients, compared with BiV pacing off. When directly comparing sequential measurements with BiV pacing on and off, median increase was 7.4%. Noncardiac sources of modulation included respiratory variation (6.4%), drift from first to last baseline measurement (5.0%), and discrepancy among repeated recordings of the same pacing intervention (3.3%). Comparing test interventions to interleaved baseline measurements reduced discrepancy among recordings to 2.1%; P < .001. CONCLUSIONS: With repeated measurements of baseline state, and by comparing test interventions only to baseline measurements performed before and after, it is possible to minimize extracardiac factors and focus on the effects of test pacing interventions.

Atrial fibrillation in heart failure: drug therapies for rate and rhythm control.

Pharmacological treatment of atrial fibrillation in the context of heart failure poses numerous challenges. Management decisions are limited by contraindications to several drugs and the paucity of robust clinical trials that provide evidence-based guidance. This review proposes a structured action plan for managing atrial fibrillation coexisting with heart failure that considers published clinical guidelines and integrates recent data derived from substudies of randomized trials, including the atrial fibrillation and congestive heart failure (AF-CHF) trial. Areas of uncertainty, such as target heart rates in atrial fibrillation and upstream therapies, are also discussed.

The time course of exit and entrance block during cryoballoon pulmonary vein isolation.

AIMS: The dynamic time course of entrance and exit block during pulmonary vein isolation (PVI) is unknown. The purpose of this series was to dynamically evaluate the manifestation of entrance and exit conduction block during simultaneous circumferential PVI. METHODS AND RESULTS: Pacing manoeuvres were performed during cryoballoon ablation of left-sided pulmonary veins (PVs) in 30 consecutive patients with a history of drug-refractory paroxysmal atrial fibrillation. At the onset of ablation continuous pacing was performed from the PV at a cycle length of 600 ms until the appearance of exit block. Once exit block was demonstrated, uninterrupted pacing was immediately transitioned to the distal coronary sinus (CS) catheter and continued at 600 ms throughout the rest of the cryoapplication. The timing of exit block, entrance block, and corresponding cryoballoon temperature were noted for all patients. In the 45 PVs when real-time PV recordings were available during cryothermal ablation, the presence of exit block was reliably demonstrated to precede entrance block (P < 0.0001) by a median of 5 s [interquartile range (IQR) 3, 12; median temperature at isolation -39°C (IQR -30, -45); nadir ablation temperature -53°C (IQR -48, -59)]. In all cases, when uninterrupted pacing was transitioned from the PV to the distal CS, entrance conduction from the left atrium to PV remained intact. CONCLUSION: Circumferential PV ablation results in progressive PVI, beginning with unidirectional exit block, and followed by entrance block. As exit block reliably precedes entrance block, we are able to provide justification for the exclusive use of entrance conduction block as the endpoint of cryoballoon-based PVI.

Canadian Cardiovascular Society 2023 Guidelines on the Fitness to Drive.

Cardiovascular conditions are among the most frequent causes of impairment to drive, because they might induce unpredictable mental state alterations via diverse mechanisms like myocardial ischemia, cardiac arrhythmias, and vascular dysfunction. Accordingly, health professionals are often asked to assess patients' fitness to drive (FTD). The Canadian Cardiovascular Society previously published FTD guidelines in 2003-2004; herein, we present updated FTD guidelines. Because there are no randomized trials on FTD, observational studies were used to estimate the risk of driving impairment in each situation, and recommendations made on the basis of Canadian Cardiovascular Society Risk of Harm formula. More restrictive recommendations were made for commercial drivers, who spend longer average times behind the wheel, use larger vehicles, and might transport a larger number of passengers. We provide guidance for individuals with: (1) active coronary artery disease; (2) various forms of valvular heart disease; (3) heart failure, heart transplant, and left ventricular assist device situations; (4) arrhythmia syndromes; (5) implantable devices; (6) syncope history; and (7) congenital heart disease. We suggest appropriate waiting times after cardiac interventions or acute illnesses before driving resumption. When short-term driving cessation is recommended, recommendations are on the basis of expert consensus rather than the Risk of Harm formula because risk elevation is expected to be transient. These recommendations, although not a substitute for clinical judgement or governmental regulations, provide specialists, primary care providers, and allied health professionals with a comprehensive list of a wide range of cardiac conditions, with guidance provided on the basis of the level of risk of impairment, along with recommendations about ability to drive and the suggested duration of restrictions.