Transvenous versus subcutaneous implantable cardioverter defibrillators in young cardiac arrest survivors.

Secondary prevention implantable cardioverter defibrillators (ICDs) are indicated in young patients presenting with aborted sudden cardiac death (SCD) because of ventricular arrhythmias. Transvenous-ICDs (TV-ICDs) are effective, established therapies supported by evidence. The significant morbidity associated with transvenous leads led to the development of the newer subcutaneous-ICD (S-ICD). This review discusses the clinical considerations when selecting an ICD for the young patient presenting with out-of-hospital cardiac arrest. The major benefits of TV-ICDs are their ability to pace (antitachycardia pacing [ATP], bradycardia support and cardiac resynchronisation therapy [CRT]) and the robust evidence base supporting their use. Other benefits include a longer battery life. Significant complications associated with transvenous leads include pneumothorax and tamponade during insertion and infection and lead failure in the long term. Comparatively, S-ICDs, by virtue of having no intravascular leads, prevent these complications. S-ICDs have been associated with a higher incidence of inappropriate shocks. Patients with an indication for bradycardia pacing, CRT or ATP (documented ventricular tachycardia) are seen as unsuitable for a S-ICD. If venous access is unsuitable or undesirable, S-ICDs should be considered given the patient is appropriately screened. There is a need for further randomised controlled trials to directly compare the two devices. TV-ICDs are an effective therapy for preventing SCD limited by significant lead-related complications. S-ICDs are an important development hindered largely by an inability to pace. Young patients stand to gain the most from a S-ICD as the cumulative risk of lead-related complications is high. A clinical framework to aid decision-making is presented.

Subcutaneous defibrillator use with unipolar pacemakers: Cautiously possible.

Implantation of subcutaneous implantable cardioverter-defibrillator in a patient with existing unipolar pacemaker is against manufacturer recommendations. We report the case of a successful subcutaneous implantable cardioverter-defibrillator implantation in a patient with Fontan circulation and concomitant active unipolar pacing and present a summary of recommendations when considering subcutaneous implantable cardioverter-defibrillator implantation with unipolar pacing. Recommendations included: pre-procedure screening, rescreening during implantation and ventricular fibrillation induction, pacemaker programming, and post-procedure investigations.

Impact of device length on electrogram sensing in miniaturized insertable cardiac monitors.

BACKGROUND: Little data exists on electrogram sensing in current generation of miniaturized insertable cardiac monitors (ICMs). OBJECTIVE: To compare the sensing capability of ICM with different vector length: Medtronic Reveal LINQ (~40 mm) vs. Biotronik Biomonitor III (BM-III, ~70 mm). METHODS: De-identified remote monitoring transmissions from n = 40 patients with BM-III were compared with n = 80 gender and body mass index (BMI)-matched patients with Reveal LINQ. Digital measurement of P- and R-wave amplitude from calibrated ICM electrograms was undertaken by 3 investigators independently. Further, we evaluated the impact of BMI and gender on P-wave visibility. RESULTS: Patients in both groups were well matched for gender and BMI (53% male, mean BMI 26.7 kg/m2, both p = NS). Median P- and R-wave amplitude were 97% & 56% larger in the BM-III vs. LINQ [0.065 (IQR 0.039-0.10) vs. 0.033 (IQR 0.022-0.050) mV, p < .0001; & 0.78 (IQR 0.52-1.10) vs. 0.50 (IQR 0.41-0.89) mV, p = .012 respectively). The P/R-wave ratio was 36% greater with the BM-III (p < .001). The 25th percentile of P-wave amplitude for all 120 patients was .026 mV. Logistic regression analysis showed BM-III was more likely than LINQ to have P-wave amplitude ≥.026 mV (OR 7.47, 95%CI 1.965-29.42, p = .003), and increasing BMI was negatively associated with P-wave amplitude ≥.026 mV (OR 0.84, 95%CI 0.75-0.95, p = .004). However, gender was not significantly associated with P-wave amplitude ≥.026 mV (p = .37). CONCLUSION: The longer ICM sensing vector of BM-III yielded larger overall P- and R- wave amplitude than LINQ. Both longer sensing vector and lower BMI were independently associated with greater P-wave visibility.

Prediction of Pacemaker Requirement in Patients With Unexplained Syncope: The DROP Score.

BACKGROUND: Implantable loop recorders (ILR) are increasingly utilised in the evaluation of unexplained syncope. However, they are expensive and do not protect against future syncope. OBJECTIVES: To compare patients requiring permanent pacemaker (PPM) implantation during ILR follow-up with those without abnormalities detected on ILR in order to identify potential predictors of benefit from upfront pacing. METHODS: We analysed 100 consecutive patients receiving ILR: Group 1 (n=50) underwent PPM insertion due to bradyarrhythmias detected on ILR; Group 2 (n=50) had no arrhythmias detected on ILR over >3 years follow-up. Baseline clinical characteristics, syncope history, electrocardiographic and echocardiographic parameters were assessed to identify predictors of ultimate requirement for pacing. RESULTS: Group 1 (64% male, median age 70.8 years; IQR 65.5-78.8) were older than Group 2 (58% male, median 60.2 years; IQR 44.0-73.0 p=0.001) and were less likely to have related historical factors such as overheating, posture and exercise (98% vs 70% p<0.001). PR interval was also longer in Group 1 (192±51 vs 169±23 p=0.006) with greater prevalence of distal conduction system disease (30% vs 4.3% p=0.002). Significant univariate predictors for PPM insertion were distal conduction disease (p=0.007), first degree atrioventricular (AV) block (p=0.003), absence of precipitating factors (p=0.004), and age >65 years (p=0.001). Injury sustained, recurrent syncope, history of atrial fibrillation (AF) or heart failure, left atrial (LA) size and left ventricular ejection fraction (LVEF) were not predictive. These significant predictors were incorporated into the DROP score1 (0-4). Using time-to-event analysis, no patients with a score of 0 progressed to pacing, while higher scores (3-4) strongly predicted pacing requirement (log-rank p<0.001). CONCLUSION: The DROP score may be helpful in identifying patients likely to benefit from upfront permanent pacemaker (PPM) insertion following unexplained syncope. Larger prospective studies are required to validate this tool.

Long-Term Implications of Pacemaker Insertion in Younger Adults: A Single Centre Experience.

BACKGROUND: The long-term implications of pacemaker insertion in younger adults are poorly described in the literature. METHODS: We performed a retrospective analysis of consecutive younger adult patients (18-50 yrs) undergoing pacemaker implantation at a quaternary hospital between 1986-2020. Defibrillators and cardiac resynchronisation therapy devices were excluded. All clinical records, pacemaker checks and echocardiograms were reviewed. RESULTS: Eighty-one (81) patients (median age 41.0 yrs IQR=35-47.0, 53% male) underwent pacemaker implantation. Indications were complete heart block (41%), sinus node dysfunction (33%), high grade AV block (11%) and tachycardia-bradycardia syndrome (7%). During a median 7.9 (IQR=1.1-14.9) years follow-up, nine patients (11%) developed 13 late device-related complications (generator or lead malfunction requiring reoperation [n=11], device infection [n=1] and pocket revision [n=1]). Five (5) of these patients were <40 years old at time of pacemaker insertion. At long-term follow-up, a further nine patients (11%) experienced pacemaker-related morbidity from inadequate lead performance managed with device reprogramming. Sustained ventricular tachycardia was detected in two patients (2%). Deterioration in ventricular function (LVEF decline >10%) was observed in 14 patients (17%) and seven of these patients required subsequent biventricular upgrade. Furthermore, four patients (5%) developed new tricuspid regurgitation (>moderate-severe). Of 69 patients with available long-term pacing data, minimal pacemaker utilisation (pacing <5% at all checks) was observed in 13 (19%) patients. CONCLUSIONS: Pacemaker insertion in younger adults has significant long-term implications. Clinicians should carefully consider pacemaker insertion in this cohort given risk of device-related complications, potential for device under-utilisation and issues related to lead longevity. In addition, patients require close follow-up for development of structural abnormalities and arrhythmias.

Prescription trends and costs of diabetes medications in Australia between 2003 and 2019: an analysis and review of the literature.

BACKGROUND: Since the turn of the century, the prevalence of diabetes mellitus in Australia has increased, primarily due to rising rates of Type 2 diabetes. Simultaneously, the landscape of diabetes medications has evolved significantly. The change in prescribing trends and public spending on diabetes medications within Australia during this period are not well defined. AIMS: To establish the frequency and cost of dispensed diabetes medications in the Australian public healthcare system between 2003 and 2019. METHODS: We performed a longitudinal nationwide observational study using data obtained from the Pharmaceutical Benefits Scheme (PBS) and Medicare Benefits Schedule websites, which contain information on frequency and spending of diabetes medications dispensed in Australia. RESULTS: The total number of PBS-subsidised prescriptions dispensed for diabetes increased from 5 218 690 in 2003 to 12 188 568 in 2019, and spending increased from $117 241 031 to $598 904 983. Of the non-insulin agents, metformin was consistently the most frequently dispensed agent, with a rapid growth in metformin combination tablets. Dispensation of sulphonylureas and thiazolidinediones have declined, with a simultaneous increase in dipeptidyl peptidase-4 inhibitors, sodium-glucose co-transporter 2 inhibitors and glucagon-like peptide-1 receptor agonists. CONCLUSIONS: Our data show a large growth in the use of diabetes medications between 2003 and 2019. The rapid growth in dispensing of drugs with proven cardiovascular and renal benefits reflect the evolving approach of diabetes treatment, from a historical approach targeting glycaemic control alone, to a modern individualised approach targeting specific co-morbidities.

A prospective STudy using invAsive haemodynamic measurements foLLowing catheter ablation for AF and early HFpEF: STALL AF-HFpEF.

AIMS: The impact of atrial fibrillation (AF) ablation in early heart failure with preserved ejection fraction (HFpEF) is unknown. Our aim was to determine the impact of AF ablation on symptoms and exercise haemodynamic parameters of early HFpEF. METHODS AND RESULTS: Symptomatic AF patients referred for index AF ablation with ejection fraction ≥50% underwent baseline quality of life questionnaires, echocardiography, cardiac magnetic resonance imaging, exercise right heart catheterisation (exRHC), and brain natriuretic peptide (BNP) testing. HFpEF was defined by resting pulmonary capillary wedge pressure (PCWP) ≥15 mmHg or peak exercise PCWP ≥25 mmHg. Patients with HFpEF were offered AF ablation and follow-up exRHC ≥6 months post-ablation. Of 54 patients undergoing baseline evaluation, 35 (65%) had HFpEF identified by exRHC. HFpEF patients were older (64 ± 10 vs. 54 ± 13 years, P < 0.01), and more frequently female (54% vs. 16%, P < 0.01), hypertensive (63% vs. 16%, P < 0.001), and suffering persistent AF (66% vs. 11%, P < 0.001), compared to those without HFpEF. Twenty HFpEF patients underwent AF ablation and follow-up exRHC 12 ± 6 months post-ablation. Nine (45%) patients no longer fulfilled exRHC criteria for HFpEF at follow-up. Patients remaining arrhythmia free (n = 9, 45%) showed significant improvements in peak exercise PCWP (29 ± 4 to 23 ± 2 mmHg, P < 0.01) and Minnesota Living with Heart Failure (MLHF) score (55 ± 30 to 22 ± 30, P < 0.01) while the remainder did not (PCWP 31 ± 5 to 30.0 ± 4 mmHg, P = NS; MLHF score 55 ± 23 to 25 ± 20, P = NS). CONCLUSION: Heart failure with preserved ejection fraction frequently coexists in patients with symptomatic AF and preserved ejection fraction. Restoration and maintenance of sinus rhythm in patients with comorbid AF and HFpEF improves haemodynamic parameters, BNP and symptoms associated with HFpEF.

Rural and Remote Cardiology During the COVID-19 Pandemic: Cardiac Society of Australia and New Zealand (CSANZ) Consensus Statement.

THE CHALLENGES: Rural and remote Australians and New Zealanders have a higher rate of adverse outcomes due to acute myocardial infarction, driven by many factors. The prevalence of cardiovascular disease (CVD) is also higher in regional and remote populations, and people with known CVD have increased morbidity and mortality from coronavirus disease 2019 (COVID-19). In addition, COVID-19 is associated with serious cardiac manifestations, potentially placing additional demand on limited regional services at a time of diminished visiting metropolitan support with restricted travel. Inter-hospital transfer is currently challenging as receiving centres enact pandemic protocols, creating potential delays, and cardiovascular resources are diverted to increasing intensive care unit (ICU) and emergency department (ED) capacity. Regional and rural centres have limited staff resources, placing cardiac services at risk in the event of staff infection or quarantine during the pandemic. MAIN RECOMMENDATIONS: Health districts, cardiologists and government agencies need to minimise impacts on the already vulnerable cardiovascular health of regional and remote Australians and New Zealanders throughout the COVID-19 pandemic. Changes in management should include.

Position Statement on the Management of Cardiac Electrophysiology and Cardiac Implantable Electronic Devices in Australia During the COVID-19 Pandemic: A Living Document.

The COVID-19 pandemic poses a significant stress on health resources in Australia. The Heart Rhythm Council of the Cardiac Society of Australia and New Zealand aims to provide a framework for efficient resource utilisation balanced with competing risks when appropriately treating patients with cardiac arrhythmias. This document provides practical recommendations for the electrophysiology (EP) and cardiac implantable electronic devices (CIED) services in Australia. The document will be updated regularly as new evidence and knowledge is gained with time.

Miniaturized implantable cardiac monitor with a long sensing vector (BIOMONITOR III): Insertion procedure assessment, sensing performance, and home monitoring transmission success.

BACKGROUND: Implantable Cardiac Monitors (ICMs) are used for long-term monitoring of arrhythmias. BIOMONITOR III is a novel ICM with a miniaturized profile, long sensing vector due to a flexible antenna, simplified implantation with a dedicated insertion tool for pocket formation and ICM placement in a single step, and daily automatic Home Monitoring (HM) function. METHODS: In 47 patients undergoing BIOMONITOR III insertion for any ICM indication, 16 investigators at 10 Australian sites assessed handling characteristics of the insertion tool, R-wave amplitudes, noise burden, P-wave visibility, and HM transmission success. Patients were followed for 1 month. RESULTS: All 47 attempted insertions were successful. Median time from skin incision to removal of the insertion tool after ICM insertion was 39 s (IQR 19-65) and to wound closure and cleaning was 4.7 min (IQR 3.5-7.8). All aspects of the insertion tool were rated as "good" or "excellent" in ≥97.9% and "fair" in ≤2.1% of patients, except for "force needed for tunnelling" (91.5% good/excellent, 8.5% fair). Based on HM data, R-waves in the first month were stable at 0.70 ± 0.37 mV. Median noise burden (disabling automatic rhythm evaluation) was 0.19% (IQR 0.00-0.93), equivalent to 2.7 min (IQR 0.0-13.4) per day. In HM-transmitted ECG strips with regular sinus rhythm, P-waves were visible in 89 ± 24% of heart cycles. Patient-individual automatic Home Monitoring transmission success was 98.0% ± 5.5%. CONCLUSIONS: The novel ICM performed well in all aspects studied, including fast insertion, reliable R-wave sensing, good P-wave visibility, and highly successful HM transmissions.

The effect of parity on exercise physiology in women with heart failure with preserved ejection fraction.

AIMS: Women are overrepresented amongst patients with heart failure with preserved ejection fraction (HFpEF); however, the underpinning mechanism for this asymmetric distribution is unclear. Pregnancy represents a potential gender-specific risk factor for HFpEF. It leads to significant physiological adaption, and increasing parity has been associated with some cardiovascular risk. We sought to examine the relationship between prior parity with the rest and exercise haemodynamic and echocardiographic profile of women with HFpEF. METHODS AND RESULTS: Patients referred for assessment of exertional dyspnoea and confirmed to have a haemodynamic and clinical profile consistent with HFpEF were included. Detailed evaluation consisted of rest and exercise right heart catheterization and echocardiography. A socio-economic and obstetric history was also documented. Fifty-eight women were assessed and categorized as having either 0-2 births or ≥3 births, dividing the cohort equally. Women with ≥3 births achieved a lower symptom-limited workload than those with 0-2 births [38 (24-51) vs. 46 (31-68) W, P = 0.04]. Women with ≥3 births had a greater rise in pulmonary capillary wedge pressure indexed to workload with exercise [0.5 (0.3-0.8) vs. 0.3 (0.2-0.5) mmHg/W, P = 0.03], paralleled by a greater rise in right atrial pressure [10 (8-12) vs. 7 (3-11), P = 0.01]. Pulmonary vascular resistance was also higher in women with ≥3 births [1.9 (1.6-2.4) vs. 1.6 (1.4-1.9) mmHg/L/min rest, P = 0.046, and 1.9 (2.4-2.4) vs. 1.4 (1-1.8) mmHg/L/min exercise, P = 0.024]. Left ventricular ejection fraction was lower at rest [60 (57-61) vs. 63 (60-66), P = 0.008] and during exercise [65 (62-67) vs. 68 (66-70), P = 0.038] in women with higher parity. CONCLUSIONS: Higher parity is associated with greater impairments in multiple physiologic parameters of HFpEF severity in women, including diastolic reserve, pulmonary vascular resistance, and systolic dysfunction.

Driving with cardiac devices in Australia. Does a review of recent evidence prompt a change in guidelines?

Australian Driving Guidelines for patients with pacemakers and implanted cardioverter defibrillators are in line with many around the world, with some minor differences. Some aspects of these guidelines lack contemporary evidence in key decision-making areas and make broad recommendations regarding groups with heterogeneous populations. In addition, more recent studies suggest lower rates of adverse events in some patients with these devices than previously thought. Through a systematic literature review, along with discussion of current guidelines, we combine new evidence with well established risk assessment tools to ask the following questions: (i) Given the heterogeneity of patient risk within the defibrillator population, should guidelines allow for further individualisation of risk and subsequent licensing restrictions?; and (ii) Could some patients with primary prevention automated cardioverter defibrillators be able to hold a commercial driving licence?

Increased Incidence of Noise in the Tendril Pacemaker Lead Detected via Remote Monitoring.

BACKGROUND: Prior studies suggest increased rates of noise on the Tendril (St Jude Medical/Abbott, St. Paul, MN, USA) pacemaker lead. We aim to assess the incidence of lead noise in the Tendril and 5076 (Medtronic PLC, Minneapolis, MN, USA) pacemaker leads in our cohort and in the process assess the utility of remote monitoring for identifying lead malfunction. METHODS: Deidentified, multi-centre, prospectively collected observational cohort data was obtained to assess the incidence of noise on the Tendril and 5076 pacemaker leads. RESULTS: 148 Tendril and 737 CapSureFix Novus 5076 (Medtronic, MN, USA) pacemaker leads were remotely monitored. Incidence of noise on the Tendril was 8% and 0.27% on the CapSureFix Novus. CONCLUSION: Rates of noise in the Tendril lead are higher than a market competitor. Remote monitoring is useful in detecting this concerning anomaly.

A Retrospective Evaluation of Risk of Peripartum Cardiac Dysfunction in Survivors of Childhood, Adolescent and Young Adult Malignancies.

Long-term survivors of childhood, adolescent and young adult (AYA) malignancies with past exposure to potentially cardiotoxic treatments are at risk of peripartum cardiac dysfunction. Incidence and risk factors for peripartum cardiac dysfunction and maternal cardiac outcomes in this population were investigated. Eligible long-term survivors were aged <30 years at cancer diagnosis, with ≥1 pregnancy occurring ≥5 years after diagnosis. "Peripartum" cardiac events were defined as occurring within pregnancy or ≤5months after delivery. Cardiac events were classified "symptomatic" or "subclinical". "Peripartum cardiomyopathy" (PPCM) was defined as symptomatic dysfunction without prior cardiac dysfunction. Of 64 eligible women, 5 (7.8%) had peripartum cardiac events: 3 symptomatic, 2 subclinical. Of 110 live births, 2 (1.8%, 95% CI 0.2-6.4) were defined as PPCM: Significantly greater than the published general population incidence of 1:3000 (p < 0.001), representing a 55-fold (95% CI 6.6-192.0) increased risk. Risk factor analyses were hypothesis-generating, revealing younger age at cancer diagnosis and higher anthracycline dose. Postpartum, cardiac function of 4 women (80%) failed to return to baseline. In conclusion, peripartum cardiac dysfunction is an uncommon but potentially serious complication in long-term survivors of paediatric and AYA malignancies previously treated with cardiotoxic therapies. Peripartum cardiac assessment is strongly recommended for at-risk patients.

Sex Differences in Heart Failure With Preserved Ejection Fraction Pathophysiology: A Detailed Invasive Hemodynamic and Echocardiographic Analysis.

OBJECTIVES: This study sought to identify sex differences in central and peripheral factors that contribute to the pathophysiology of heart failure with preserved ejection fraction (HFpEF) by using complementary invasive hemodynamic and echocardiographic approaches. BACKGROUND: Women are overrepresented among patients with HFpEF, and there are established sex differences in myocardial structure and function. Exercise intolerance is a fundamental feature of HFpEF; however, sex differences in the physiological determinants of exercise capacity in HFpEF are yet to be established. METHODS: Patients with exertional intolerance with confirmed HFpEF were included in this study. Evaluation of the subjects included resting and exercise hemodynamics, echocardiography, and mixed venous blood gas sampling. RESULTS: A total of 161 subjects included 114 females (71%). Compared to males, females had a higher pulmonary capillary wedge pressure (PCWP) indexed to peak exercise workload (0.8 [0.5 to 1.2] mm Hg/W vs. 0.6 [0.4 to 1] mm Hg/W, respectively; p = 0.001) and lower systemic (1.1 [0.9 to 1.5] ml/mm Hg vs. 1 [0.7 to 1.2] ml/mm Hg, respectively; p = 0.019) and pulmonary (2.9 [2.2 to 4.2] ml/mm Hg vs. 2.4 [1.9 to 3] ml/mm Hg, respectively; p = 0.032) arterial compliance at exercise. Mixed venous blood gas analysis demonstrated a greater rise in lactate indexed to peak workload (0.05 [0.04 to 0.09] mmol/l/W vs. 0.04 [0.03 to 0.06] mmol/l/W, respectively; p = 0.007) in women compared to men. Women had higher mitral inflow velocity to diastolic mitral annular velocity at early filling (E/e') ratios at rest and peak exercise, along with a higher ejection fraction and smaller ventricular dimensions. CONCLUSIONS: Women with HFpEF demonstrate poorer diastolic reserve with higher echocardiographic and invasive measurements of left ventricular filling pressures at exercise, accompanied by lower systemic and pulmonary arterial compliance and poorer peripheral oxygen kinetics.

Impaired left atrial strain predicts abnormal exercise haemodynamics in heart failure with preserved ejection fraction.

BACKGROUND: Elevated left atrial (LA) pressure, particularly during exercise, is associated with symptomatic status and survival in patients with heart failure with preserved ejection fraction (HFpEF). We aimed to characterize the contribution of abnormal LA mechanical properties to exercise haemodynamics in HFpEF. METHODS AND RESULTS: Simultaneous echocardiography and right heart catheterization were performed in 71 subjects with left ventricular ejection fraction ≥ 50% referred for assessment of exertional dyspnoea. According to haemodynamic evaluation, 49 patients were diagnosed with HFpEF [pulmonary capillary wedge pressure (PCWP) ≥ 15 mmHg at rest and/or ≥ 25 mmHg at maximal exertion] and 22 as non-cardiac dyspnoea. Apical two- and four-chamber views were used for blinded two-dimensional LA speckle tracking analysis. HFpEF was characterized by impaired LA reservoir (24.3 ± 9.6 vs. 36.7 ± 8.4%, P < 0.001) and pump strain (-11.5 ± 3.2 vs. -17.0 ± 3.4%, P < 0.001); and increased stiffness (0.8 ± 0.7 vs. 0.2 ± 0.1 mmHg/%, P < 0.001). Reservoir and pump strain correlated with exercise PCWP (r = -0.64 and r = 0.72, P < 0.001), and remained independent predictors after adjusting for left ventricular mass index, LA volume index, mean E/e' and systolic blood pressure (B = -0.66 and B = 1.41, respectively, P < 0.001). LA stiffness was strongly related to B-type natriuretic peptide levels (r = 0.73, P < 0.001; B = 173.0, P < 0.001). Reservoir strain at cut-off of ≤ 33% predicted invasively verified HFpEF diagnosis with 88% sensitivity and 77% specificity, providing a net reclassification improvement of 12% in comparison to the 2016 European Society of Cardiology criteria for non-invasive diagnosis of HFpEF. CONCLUSIONS: Impaired LA reservoir and pump function and increased stiffness are associated with abnormal exercise haemodynamics in HFpEF. These markers provide significant HFpEF diagnostic utility in elderly ambulatory patients with dyspnoea.

Absence of late gadolinium enhancement on cardiac magnetic resonance imaging in ventricular fibrillation and nonischemic cardiomyopathy.

INTRODUCTION: Cardiac magnetic resonance (CMR)-identified late gadolinium enhancement (LGE), representing regional fibrosis, is often used to predict ventricular arrhythmia risk in nonischemic cardiomyopathy (NICM). However, LGE is more closely correlated with sustained monomorphic ventricular tachycardia (SMVT) than ventricular fibrillation (VF). We characterized CMR findings of ventricular LGE in VF survivors. METHODS: We examined consecutively resuscitated VF survivors undergoing contrast-enhanced 1.5T CMR between 9/2007 and 7/2016. We excluded coronary artery disease, hypertrophic cardiomyopathy, amyloid, sarcoid, arrhythmogenic right ventricular cardiomyopathy, and channelopathy. Preexisting implantable cardioverter-defibrillator (ICD) was a CMR contraindication. VF patients were divided into three groups: (1) NICM, (2) left ventricular (LV) dilatation with normal LV ejection fraction (LVEF), and (3) normal LV size and LVEF. Two groups of NICM patients with and without SMVT were examined for comparison. RESULTS: We analyzed 87 VF patients, and found that LGE was seen in 8/22 (36%) with NICM (LVEF 38 ± 11%, LV end-diastolic volume index [LVEDVI] 134 ± 68 mL/BSA), 11/40 (28%) with LV dilatation and normal LVEF (LVEDVI 103 ± 17 mL/BSA), 4/25 (16%) with normal LV size and LVEF. Incidence of LGE in NICM patients without prior ventricular tachycardia/VF (LVEF 36 ± 12%, LVEDVI 141 ± 46 mL/body surface area [BSA]) was 117/277 and was not lower than those with VF and NICM (42% vs 36%; P = 0.59). By contrast, 22/37 NICM patients with SMVT (LVEF 42 ± 11%, LVEDVI 123 ± 48 mL/BSA) were LGE-positive (59% NICM-SMVT vs 36% NICM-VF; P = 0.04). CONCLUSION: Most VF survivors with a diagnosis of NICM did not have LGE on CMR and would not have met primary prevention ICD criteria based on LVEF. Absence of LGE may not portend a benign prognosis in NICM. Novel strategies for determining SCD risk in this cohort are required.