Cardiac resynchronization therapy-induced proarrhythmia: understanding preferential conduction within myocardial scars

The Effects of His Bundle Pacing Compared to Classic Resynchronization Therapy in Patients with Pacing-Induced Cardiomyopathy

Pacing-induced cardiomyopathy (PICM) is among the most common right ventricular pacing complications. Upgrading to cardiac resynchronization therapy (CRT) is the recommended treatment option. Conduction system pacing with His bundle pacing (HBP) has the potential to restore synchronous ventricular activation and can be an alternative to biventricular pacing (BVP). Patients with PICM scheduled for a system upgrade to CRT were included in the prospective cohort study. Either HBP or BVP was used for CRT. Electrocardiographic, clinical, and echocardiographic measurements were recorded at baseline and six-month follow-up. HBP was successful in 44 of 53 patients (83%). Thirty-nine patients with HBP and 22 with BVP completed a 6-month follow-up. HBP led to a higher reduction in QRS duration than BVP, 118.3 ± 14.20 ms vs. 150.5 ± 18.64 ms, p < 0.0001. The improvement in New York Heart Association (NYHA) class by one or two was more common in patients with HBP than those with BiV (p = 0.04). Left ventricular ejection fraction (LVEF) improved in BVP patients from 32.9 ± 7.93% to 43.9 ± 8.07%, p < 0.0001, and in HBP patients from 34.9 ± 6.45% to 48.6 ± 7.73%, p < 0.0001. The improvement in LVEF was more considerable in HBP patients than in BVP patients, p = 0.019. The improvement in clinical outcomes and left ventricle reverse remodeling was more significant with HBP than BVP. HBP can be a valid alternative to BVP for upgrade procedures in PICM patients.

Left ventricular pacing induced polymorphic ventricular tachycardia via the adaptive left ventricle pacing algorithm

Providers should be aware of the possibility of cardiac resynchronization therapy-related proarrhythmia which could be life-threatening. His-bundle pacing may serve as an alternative, more physiological, option in the management as it preserves the normal sequence of depolarization from the septum to the lateral wall, and from endocardium to epicardium.

Anomalous right coronary artery with interarterial course depicting an unusual case of an electrical storm: a case presentation

Background

The condition of anomalous aortic origin of the right coronary artery (AAORCA) with an interarterial course leads to few, if any, clinical problems. Malignant presentation of the often non-significant AAORCA associated with conduction system abnormalities is a rare finding. Surgical repair, even for highly symptomatic patients, is still controversial. However, in this case, the surgery brought a paradigm shift in treatment modality, improving the symptoms of this patient.

Case presentation

We report a case of a 52-year-old man with severe chest pain and recurrent electrical storms with an implanted cardiac resynchronization therapy defibrillator (CRT-D) device. Coronary angiography and computed tomography (CT) revealed the rare anomalous aortic origin of the right coronary artery (AAORCA) with a high interarterial course between the aorta and the pulmonary trunk. As symptoms typically develop on exertion, placing the patient at an increased risk of ischemic distress, a stress myocardial perfusion imaging study helped to identify his high-risk status. Although patient-specific, a surgical repair was the only concrete step agreed upon after multiple collaborative discussions with the cardiac surgeons. Surgery significantly improved the symptoms, with the patient reporting resolution of his chest pain, as well as no documented inappropriate defibrillator activity on follow-up appointments.

Conclusion

One purpose of reporting the case study was to underscore the risk factors associated with AAORCA, challenging claims of its benign nature. This case complements existing findings demonstrating that ischemic distress consequent to the right coronary artery (RCA) compression may precede the rare incidence of an electrical storm. Importantly, the case-study emphasizes the significance of integrated multimodality imaging in clinical practice as well as providing real-world evidence for the efficacy of surgical repair in highly symptomatic patients with AAORCA with an interarterial course.

Cardiac Resynchronisation Therapy and Cellular Bioenergetics: Effects Beyond Chamber Mechanics

Cardiac resynchronisation therapy is a cornerstone in the treatment of advanced dyssynchronous heart failure. However, despite its widespread clinical application, precise mechanisms through which it exerts its beneficial effects remain elusive. Several studies have pointed to a metabolic component suggesting that, both in concert with alterations in chamber mechanics and independently of them, resynchronisation reverses detrimental changes to cellular metabolism, increasing energy efficiency and metabolic reserve. These actions could partially account for the existence of responders that improve functionally but not echocardiographically. This article will attempt to summarise key components of cardiomyocyte metabolism in health and heart failure, with a focus on the dyssynchronous variant. Both chamber mechanics-related and -unrelated pathways of resynchronisation effects on bioenergetics – stemming from the ultramicroscopic level – and a possible common underlying mechanism relating mechanosensing to metabolism through the cytoskeleton will be presented. Improved insights regarding the cellular and molecular effects of resynchronisation on bioenergetics will promote our understanding of non-response, optimal device programming and lead to better patient care.

Sudden Cardiac Death Substrate Imaged by Magnetic Resonance Imaging: From Investigational Tool to Clinical Applications

Sudden cardiac death (SCD) is a devastating event afflicting 350 000 Americans annually despite the availability of life-saving preventive therapy, the implantable cardioverter defibrillator. SCD prevention strategies are hampered by over-reliance on global left ventricular ejection fraction <35% as the most important criterion to determine implantable cardioverter defibrillator candidacy. Annually in the United States alone, this results in ≈130 000 implantable cardioverter defibrillator placements at a cost of >$3 billion but only a 5% incidence per year of appropriate firings. This approach further fails to identify individuals who experience the majority, as many as 80%, of SCD events, which occur in the setting of more preserved left ventricular ejection fraction. Better risk stratification is needed to improve care and should be guided by direct pathophysiologic markers of arrhythmic substrate, such as specific left ventricular structural abnormalities. There is an increasing body of literature to support the prognostic value of cardiac magnetic resonance imaging with late gadolinium enhancement in phenotyping the left ventricular to identify those at highest risk for SCD. Cardiac magnetic resonance has unparalleled tissue characterization ability and provides exquisite detail about myocardial structure and composition, abnormalities of which form the direct, pathophysiologic substrate for SCD. Here, we review the evolution and the current state of cardiac magnetic resonance for imaging the arrhythmic substrate, both as a research tool and for clinical applications.