Complete atrioventricular block persisting after regression of infectious myocarditis

Influenza associated cardiac arrhythmia- a systematic review

BACKGROUND

Influenza infection is rarely associated with cardiac conduction disorder. Cardiac arrhythmias due to such an infection have a full spectrum with ventricular arrythmias being the most common.

METHODS

In our systematic review from PubMed, OVID Medline and EMBASE we have identified 23 articles describing arrythmias associated with different influenza infection. Most of them were case reports where ventricular arrhythmias were the most common.

RESULTS

Complete heart block after influenza infection is usually temporary and a permanent pacemaker is rarely needed. There are reports of Influenza associated with arrhythmias in adults, neonates, and even fetuses in pregnant woman. Different mechanisms were described in literatures by which influenza causes arrhythmias such as interleukin 6 & tumor necrosis factor-alpha mediated inflammatory response, sympathetic overactivation, focal myocarditis and cleavage of angiotensin converting enzyme 2 protein which is cardioprotective.

CONCLUSIONS

ACE 2 binder influenza viruses have more prone to be associated with cardiac conduction disorder. Oseltamivir for influenza infection is also associated with bradycardia and can shorten or lengthen QT segment. Influenza vaccination has found to be protective from cardiac arrhythmia.

Update on Myocarditis: From Etiology and Clinical Picture to Modern Diagnostics and Methods of Treatment

Although the frequency of myocarditis in the general population is very difficult to accurately determine due to the large number of asymptomatic cases, the incidence of this disease is increasing significantly due to better defined criteria for diagnosis and the development of modern diagnostic methods. The multitude of different etiological factors, the diversity of the clinical picture, and the variability of the diagnostic findings make this disease often demanding both for the selection of the diagnostic modality and for the proper therapeutic approach. The previously known most common viral etiology of this disease is today overshadowed by new findings based on immune-mediated processes, associated with diseases that in their natural course can lead to myocardial involvement, as well as the iatrogenic cause of myocarditis, which is due to use of immune checkpoint inhibitors in the treatment of cancer patients. Suspecting that a patient with polymorphic and non-specific clinical signs and symptoms, such as changes in ECG and echocardiography readings, has myocarditis is the starting point in the diagnostic algorithm. Cardio magnetic resonance imaging is non-invasive and is the gold standard for diagnosis and clinical follow-up of these patients. Endomyocardial biopsy as an invasive method is the diagnostic choice in life-threatening cases with suspicion of fulminant myocarditis where the diagnosis has not yet established or there is no adequate response to the applied therapeutic regimen. The treatment of myocarditis is increasingly demanding and includes conservative methods of treating heart failure, immunomodulatory and immunospressive therapy, methods of mechanical circulatory support, and heart transplantation. The goal of developing new diagnostic and therapeutic methods is to reduce mortality from this complex disease, which is still high.

Role of Non-Myocyte Gap Junctions and Connexin Hemichannels in Cardiovascular Health and Disease: Novel Therapeutic Targets?

The heart is a complex organ composed of multiple cell types, including cardiomyocytes and different non-myocyte populations, all working closely together to determine the hearts properties and maintain normal cardiac function. Connexins are abundantly expressed proteins that form plasma membrane hemichannels and gap junctions between cells. Gap junctions are intracellular channels that allow for communication between cells, and in the heart they play a crucial role in cardiac conduction by coupling adjacent cardiomyocytes. Connexins are expressed in both cardiomyocytes and non-myocytes, including cardiac fibroblasts, endothelial cells, and macrophages. Non-myocytes are the largest population of cells in the heart, and therefore it is important to consider what roles connexins, hemichannels, and gap junctions play in these cell types. The aim of this review is to provide insight into connexin-based signalling in non-myocytes during health and disease, and highlight how targeting these proteins could lead to the development of novel therapies. We conclude that connexins in non-myocytes contribute to arrhythmias and adverse ventricular remodelling following myocardial infarction, and are associated with the initiation and development of atherosclerosis. Therefore, therapeutic interventions targeting these connexins represent an exciting new research avenue with great potential.

Late recurrence of infra-Hisian complete atrioventricular block

Acquired complete atrioventricular block that is caused by infectious myocarditis is usually transient and has a favourable outcome. We report the case of a 15-year-old girl who had complete infra-Hisian atrioventricular block due to adeno viral myocarditis and received a permanent pacemaker at the age of 10 months. The pacemaker lost its function at the age of 7 years. However, she experienced a late recurrence of complete atrioventricular block 10 years later. Complete atrioventricular block is rarely recovered if it persisted for 2 weeks. Even in the patients with late recovery, long-term follow-up and pacemaker therapy are still needed.

Cardiac magnetic resonance imaging as a tool to link cardiac conduction disease to myocarditis with minimal left ventricular impairment

Myocarditis is an injury of the myocardium caused by a variety of agents. Conduction disturbances such as complete atrioventricular block (AV block) may occur as an infrequent but serious complication of myocarditis. Early detection and accurate diagnosis of myocarditis are still unresolved challenges. We present 2 cases of otherwise mild myocarditis complicated by high-degree AV block in combination with isolated delayed uptake of contrast at the septal regions in the cardiac magnetic resonance imaging. Because the AV block was persistent in both cases, permanent pacemaker implantation was necessary. Delayed enhancement in the septal area in myocarditis might be predictive of infra-Hisian AV block.

Complete atrioventricular block as a complication of varicella in children

Although varicella is a benign and self-limited disease in children, serious complications can occur. We herein report a case of a 15-month-old boy who required a permanent pacemaker because of complete atrioventricular block as a complication of varicella. Universal vaccination is warranted to prevent such a potentially fatal complication in Japan where varicella is still endemic.

The follow-up evaluation of electrocardiogram and arrhythmias in children with fulminant myocarditis

BACKGROUND

Fulminant myocarditis involves various serious arrhythmias that sometimes have lethal consequences. The purpose of the present study was to investigate the electrocardiogram findings, arrhythmogenicity and abnormalities of the cardiac conduction system in children with fulminant myocarditis.

METHODS AND RESULTS

Between 1999 and 2008, 7 consecutive patients (mean age: 7 years) who suffered from fulminant myocarditis were included in the study. A 12-lead electrocardiogram, Holter monitoring and signal-averaged electrocardiograms were performed and compared between the acute, convalescent, and recovery phases in the 4 surviving patients. Also, electrophysiologic assessment was carried out during the convalescent phase. Five out of 7 patients developed complete atrioventricular block, 3 developed ventricular tachycardia, 2 had cardiac arrest, 2 developed sinus tachycardia, 1 developed ventricular fibrillation, 1 had advanced atrioventricular block, and 1 developed sick sinus syndrome. Among the surviving patients, all arrhythmias resolved during the convalescent and remote phases. No atrial or ventricular arrhythmias were induced in any patients during the programmed stimulation study. In the convalescent phase, no arrhythmias could be induced and there were no signs of any conduction abnormalities on electrophysiological assessment.

CONCLUSIONS

Close follow-up should be performed to observe for the occurrence of any new arrhythmias and/or a decrease in cardiac function in children with fulminant myocarditis.