Beyond Conventional Cardiac Resynchronisation Therapy: A Review of Electrophysiological Options in the Management of Chronic Heart Failure.

The incidence of heart failure (HF) continues to grow and burden our health care system. Electrophysiological aberrations are common amongst patients with heart failure and can contribute to worsening symptoms and prognosis. Targeting these abnormalities with cardiac and extra-cardiac device therapies and catheter ablation procedures augments cardiac function. Newer technologies aimed to improvement procedural outcomes, address known procedural limitations and target newer anatomical sites have been trialled recently. We review the role and evidence base for conventional cardiac resynchronisation therapy (CRT) and its optimisation, catheter ablation therapies for atrial arrhythmias, cardiac contractility and autonomic modulation therapies.

ST-elevation myocardial infarction in a migrant population: a registry-based study of patient treatment and outcomes.

BACKGROUND: Internationally, a growing number of studies has identified race-related disparities in the presentation, treatment and outcomes of patients with ST-elevation myocardial infarction (STEMI). With a large migrant population, Australia presents a unique microcosm in which to study the impact of migrant status and ethnicity in STEMI patients. AIM: To investigate if first-generation migrants differed in presentation, treatment or outcomes following STEMI compared with the Australian-born population. METHODS: We conducted a retrospective observational study using data from a clinician-initiated registry. The study involved 2154 patients who presented to 12 hospitals between 2004 and 2012. Our main outcome measures included time to reperfusion, 30-day mortality and complications. RESULTS: Migrants (n = 1035, 48.8%) were more likely to be older (61 vs 58 years, P < 0.001), diabetic (29.3 vs 21.5%, P < 0.001) and have a prolonged symptom to door time (102 vs 91 min, P = 0.04). Despite lower rates of previous known ischaemic heart disease (22.5 vs 26.6%, P = 0.03), migrants had more diffuse disease (triple vessel or left main (3VD/LM): 29.8 vs 22.0%, P < 0.001) and higher troponin values (3.77 vs 3.22 µg/L, P = 0.01). We found no significant differences in hospital treatment times, intervention types or rates. Multivariate regression identified age, diabetes, female gender and multi-vessel disease as predictors of complications and death at 30 days. CONCLUSIONS: Migrants had longer pre-hospital delays and exhibited different cardiovascular risk profiles than Australian-born patients but received comparable treatment in the acute hospital setting. Higher rates of diabetes and multi-vessel coronary artery disease were seen among migrant patients, indicating a relatively higher risk population.

Early and long-term outcomes after manual and remote magnetic navigation-guided catheter ablation for ventricular tachycardia.

Aims: Remote magnetic navigation (RMN) is a safe and effective means of performing ventricular tachycardia (VT) ablation. It may have advantages over manual catheter ablation due to ease of manoeuvrability and catheter stability. We sought to compare the safety and efficacy of RMN vs. manual VT ablation. Methods and results: Retrospective study of procedural outcomes of 139 consecutive VT ablation procedures (69 RMN, 70 manual ablation) in 113 patients between 2009 and 2015 was performed. Remote magnetic navigation was associated with overall higher acute procedural success (80% vs. 60%, P = 0.01), with a trend to fewer major complications (3% vs. 9% P = 0.09). Seventy-nine patients were followed up for a median of 17.0 [interquartile range (IQR) 3.0-41.0] months for the RMN group and 15.5 (IQR 6.5-30.0) months for manual ablation group. In the ischaemic cardiomyopathy subgroup, RMN was associated with longer survival from the composite endpoint of VT recurrence leading to defibrillator shock, re-hospitalization or repeat catheter ablation and all-cause mortality; single-procedure adjusted hazard ratio (HR) 0.240 (95% CI 0.070-0.821) P = 0.023, multi-procedure HR 0.170 (95% CI 0.046-0.632) P = 0.002. In patients with implanted defibrillators, multi-procedure VT-free survival was superior with RMN, HR 0.199 (95% CI 0.060-0.657) P = 0.003. Conclusion: Remote magnetic navigation may improve clinical outcomes after catheter ablation of VT in patients with ischaemic cardiomyopathy. Further prospective clinical studies are required to confirm these findings.

Long-term arrhythmia-free survival in patients with severe left ventricular dysfunction and no inducible ventricular tachycardia after myocardial infarction.

BACKGROUND: A negative electrophysiology study (EPS) may delineate a subgroup of patients with severely impaired left ventricular ejection fraction (LVEF) whose care can be safely managed long-term without an implantable cardioverter-defibrillator. METHODS AND RESULTS: Consecutive patients treated with primary percutaneous coronary intervention for ST-segment-elevation myocardial infarction underwent early (median 4 days) LVEF assessment. Patients with LVEF ≤40% underwent EPS. A prophylactic implantable cardioverter-defibrillator was implanted for a positive (inducible monomorphic ventricular tachycardia) but not a negative (no inducible ventricular tachycardia or inducible ventricular fibrillation/flutter) EPS result. Patients who would have become eligible for a late primary prevention implantable cardioverter-defibrillator with LVEF ≤30% or ≤35% with New York Heart Association class II/III heart failure were included and analyzed according to EPS result. Patients with LVEF >40%, ineligible for EPS, were followed up as control subjects (n=1286). The primary end point was survival free of death or arrhythmia (resuscitated cardiac arrest or sustained ventricular tachycardia/ventricular fibrillation). EPS performed in 128 patients with LVEF ≤30% or with LVEF ≤35% and heart failure was negative in 63% (n=80) and positive in 37% (n=48). Implantable-cardioverter defibrillators were implanted in <0.1%, 4%, and 90% of control, EPS-negative, and EPS-positive patients, respectively. The distribution of time to death or arrhythmia was comparable in control patients and EPS-negative patients with LVEF ≤30% or with LVEF ≤35% and heart failure (P=0.738), who both differed significantly from EPS-positive patients (P<0.001). At 3 years, 91.8 ± 3.2%, 93.4 ± 1.0%, and 62.7 ± 7.5% of control, EPS-negative, and EPS-positive patients were free of death or arrhythmia, respectively. CONCLUSIONS: Revascularized patients with ST-segment-elevation myocardial infarction with severely impaired left ventricular function but no inducible ventricular tachycardia have a favorable long-term prognosis without the protection of an implantable cardioverter-defibrillator.

Acoustic signal emission monitoring as a novel method to predict steam pops during radiofrequency ablation: preliminary observations.

UNLABELLED: Steam pop is an explosive rupture of cardiac tissue caused by tissue overheating above 100 °C, resulting in steam formation, predisposing to serious complications associated with radiofrequency (RF) ablations. However, there are currently no reliable techniques to predict the occurrence of steam pops. We propose the utility of acoustic signals emitted during RF ablation as a novel method to predict steam pop formation and potentially prevent serious complications. METHODS: Radiofrequency generator parameters (power, impedance, and temperature) were temporally recorded during ablations performed in an in vitro bovine myocardial model. The acoustic system consisted of HTI-96-min hydrophone, microphone preamplifier, and sound card connected to a laptop computer. The hydrophone has the frequency range of 2 Hz to 30 kHz and nominal sensitivity in the range -240 to -165 dB. The sound was sampled at 96 kHz with 24-bit resolution. Output signal from the hydrophone was fed into the camera audio input to synchronize the video stream. An automated system was developed for the detection and analysis of acoustic events. RESULTS: Nine steam pops were observed. Three distinct sounds were identified as warning signals, each indicating rapid steam formation and its release from tissue. These sounds had a broad frequency range up to 6 kHz with several spectral peaks around 2-3 kHz. Subjectively, these warning signals were perceived as separate loud clicks, a quick succession of clicks, or continuous squeaking noise. Characteristic acoustic signals were identified preceding 80% of pops occurrence. Six cardiologists were able to identify 65% of acoustic signals accurately preceding the pop. An automated system identified the characteristic warning signals in 85% of cases. The mean time from the first acoustic signal to pop occurrence was 46 ± 20 seconds. The automated system had 72.7% sensitivity and 88.9% specificity for predicting pops. CONCLUSIONS: Easily identifiable characteristic acoustic emissions predictably occur before imminent steam popping during RF ablations. Such acoustic emissions can be carefully monitored during an ablation and may be useful to prevent serious complications during RF delivery.

Intramyocardial adiposity after myocardial infarction: new implications of a substrate for ventricular tachycardia.

BACKGROUND: Collagen has been attributed as the principal structural substrate of ventricular tachycardia (VT) after myocardial infarction (MI), even though adiposity of myocardium after MI is well recognized histologically. We investigated the effects of intramyocardial adiposity compared with collagen on electrophysiological properties, connexin43 expression, and VT induction after MI. METHODS AND RESULTS: Simultaneous left ventricular plunge-needle, noncontact mapping was performed in sheep without MI (MI-; n=5), with MI and inducible VT (MI+VT+; n=7), and with MI and no inducible VT (MI+VT-; n=8). Histological intramyocardial quantity of adipose and collagen and degree of discontinuity were coregistered with electrophysiological parameters (MI+; 290 specimens). Additional assessment of connexin43 expression was performed. Left ventricular scar contained a body mass-independent abundance of adipocytes (adipose:collagen=0.8). Increased adipose density and discontinuity contributed to a greater inverse correlation (r) with conduction velocity (r for adipose=0.39, r for discontinuity=0.45, r for collagen=0.26) and electrogram amplitude (r for adipose=0.73, r for contiguity=0.77, r for collagen=0.68) compared with collagen. Collagen density was similar between the MI+ groups (P>0.29). However, the MI+VT+ group demonstrated a significant (all P≤0.01) increase in adipose (8%) and discontinuity (qualitative) and decrease in conduction velocity (13%) and electrogram amplitude (21%) at MI borders compared with the MI+VT- group. In scar, myocytes adjacent to fibrofatty interfaces demonstrated increased connexin43 lateralization. A gradient increase in adipose was observed at sites that supported preferential presystolic VT activation and exhibited attenuation of excitation wavelength (P<0.001). CONCLUSIONS: Intramyocardial adiposity, in association with myocardial discontinuity within left ventricular scar borders, is a significant factor associated with altered electrophysiological properties, aberrant connexin43 expression, and increased propensity for VT after MI.

What is the optimal left ventricular ejection fraction cut-off for risk stratification for primary prevention of sudden cardiac death early after myocardial infarction?

AIMS: The optimal left ventricular ejection fraction (LVEF) to select patients early post myocardial infarction (MI) for risk stratification for prevention of sudden cardiac death (SCD) in the era of primary percutaneous coronary intervention (PPCI) is unknown. METHODS AND RESULTS: Consecutive patients (n = 1722) treated with PPCI for ST-elevation MI underwent early (median 4 days) LVEF assessment. An electrophysiological study (EPS) was performed if LVEF ≤40% and a prophylactic implantable-cardioverter defibrillator (ICD) implanted for a positive [inducible monomorphic ventricular tachycardia (VT)], but not a negative, result. According to an early LVEF, a primary endpoint of inducible VT at EPS and a secondary endpoint of death or arrhythmia (SCD, resuscitated cardiac arrest or ECG-documented VT/ventricular fibrillation) were determined. The proportion of patients with early LVEF >40, 36-40, 31-35, and ≤30% were 75% (n = 1286), 7% (n = 128), 8% (n = 136), and 10% (n = 172), respectively. Inducible VT occurred in 22, 25, and 40% of patients with LVEF 36-40, 31-35, and ≤30%, respectively (P = 0.014). Three-year death or arrhythmia occurred in 6.6 ± 0.8, 8.1 ± 2.6, 18.0 ± 3.4, and 37.4 ± 3.9% of patients with LVEF >40, 36-40, 31-35, and ≤30%, respectively (overall P<0.001; LVEF 36-40% vs. LVEF > 40% P = 0.265). The number of EPS-positive patients implanted with an ICD to treat one or more arrhythmic event (95% confidence interval) was 18.3 ± 2.4, 11.5 ± 3.0, and 4.2 ± 5.6 if LVEF is 36-40, 31-35, and ≤30%, respectively. CONCLUSION: A cut-off LVEF of ≤40% selects patients with a high incidence of inducible VT post-PPCI. Patients with LVEF ≤35% and inducible VT appear to derive a greater benefit from prophylactic ICD implantation due to their higher risk of death or arrhythmia.

Bipolar ablation for deep intra-myocardial circuits: human ex vivo development and in vivo experience.

AIMS: Current conventional ablation strategies for ventricular tachycardia (VT) aim to interrupt reentrant circuits by creating ablation lesions. However, the critical components of reentrant VT circuits may be located at deep intramural sites. We hypothesized that bipolar ablations would create deeper lesions than unipolar ablation in human hearts. METHODS AND RESULTS: Ablation was performed on nine explanted human hearts at the time of transplantation. Following explant, the hearts were perfused by using a Langendorff perfusion setup. For bipolar ablation, the endocardial catheter was connected to the generator as the active electrode and the epicardial catheter as the return electrode. Unipolar ablation was performed at 50 W with irrigation of 25 mL/min, with temperature limit of 50°C. Bipolar ablation was performed with the same settings. Subsequently, in a patient with an incessant septal VT, catheters were positioned on the septum from both the ventricles and radiofrequency was delivered with 40 W. In the explanted hearts, there were a total of nine unipolar ablations and four bipolar ablations. The lesion depth was greater with bipolar ablation, 14.8 vs. 6.1 mm (P < 0.01), but the width was not different (9.8 vs. 7.8 mm). All bipolar lesions achieved transmurality in contrast to the unipolar ablations. In the patient with a septal focus, bipolar ablation resulted in termination of VT with no inducible VTs. CONCLUSION: By using a bipolar ablation technique, we have demonstrated the creation of significantly deeper lesions without increasing the lesion width, compared with standard ablation. Further clinical trials are warranted to detail the risks of this technique.