Myocarditis and arrhythmia: a clinico-pathological study of conduction system based on serial section in 65 cases

Acute necrotizing eosinophilic myocarditis complicated by complete atrioventricular block promptly responded to glucocorticoid therapy

Acute myocarditis is frequently accompanied with conduction disturbances. Complete atrioventricular (AV) block may occur in acute myocarditis, but rarely in eosinophilic myocarditis. Acute necrotizing eosinophilic myocarditis, the most severe form of eosinophilic myocarditis, is generally fatal, and rarely complicated by complete AV block. We report a case of a 66-year-old woman with acute necrotizing eosinophilic myocarditis who presented with general malaise and nausea. She suddenly fell into cardiogenic shock because of complete AV block and worsened heart failure. Ultrasound cardiography revealed pericardial effusion, edematous myocardium, and reduced contractility of the left ventricle. The biopsied specimens showed marked interstitial infiltration with predominant eosinophils accompanied with myocardial necrosis. Oral administration of glucocorticoid in moderate dose promptly resolved the complete AV block, her clinical symptoms, and cardiac function. We recognized that acute necrotizing eosinophilic myocarditis can be complicated by complete AV block. Steroid therapy could be effective in the treatment of conduction disturbance as well as myocardial inflammation. <Learning objective: We experienced a case of acute necrotizing eosinophilic myocarditis complicated by complete atrioventricular block. This case report documents the rare complication of acute necrotizing eosinophilic myocarditis and the great benefit of early steroid therapy for the condition.>.

Generation of cardiac pacemaker cells by programming and differentiation

A number of diseases are caused by faulty function of the cardiac pacemaker and described as "sick sinus syndrome". The medical treatment of sick sinus syndrome with electrical pacemaker implants in the diseased heart includes risks. These problems may be overcome via "biological pacemaker" derived from different adult cardiac cells or pluripotent stem cells. The generation of cardiac pacemaker cells requires the understanding of the pacing automaticity. Two characteristic phenomena the "membrane-clock" and the "Ca(2+)-clock" are responsible for the modulation of the pacemaker activity. Processes in the "membrane-clock" generating the spontaneous pacemaker firing are based on the voltage-sensitive membrane ion channel activity starting with slow diastolic depolarization and discharging in the action potential. The influence of the intracellular Ca(2+) modulating the pacemaker activity is characterized by the "Ca(2+)-clock". The generation of pacemaker cells started with the reprogramming of adult cardiac cells by targeted induction of one pacemaker function like HCN1-4 overexpression and enclosed in an activation of single pacemaker specific transcription factors. Reprogramming of adult cardiac cells with the transcription factor Tbx18 created cardiac cells with characteristic features of cardiac pacemaker cells. Another key transcription factor is Tbx3 specifically expressed in the cardiac conduction system including the sinoatrial node and sufficient for the induction of the cardiac pacemaker gene program. For a successful cell therapeutic practice, the generated cells should have all regulating mechanisms of cardiac pacemaker cells. Otherwise, the generated pacemaker cells serve only as investigating model for the fundamental research or as drug testing model for new antiarrhythmics. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Prevalence and clinical relevance of the morphological substrate of ventricular arrhythmias in patients without known cardiac conditions detected by cardiovascular MR

OBJECTIVE

Cardiac MR (CMR) identifies the substrate of ventricular arrhythmia (VA) in cardiomyopathies and coronary heart disease. However, little is known about the value of CMR in patients with VA without previously known cardiac disorders.

METHODS

76 patients with VA (Lown ≥2) without known cardiac disease after regular diagnostic work-up were studied with CMR, and findings were correlated with electrocardiogram (ECG) and electrophysiological stimulation (EPS). Structural abnormalities matching the VA origin as defined by ECG and/or EPS, or a CMR-detected cardiac condition known to cause arrhythmia were defined as VA substrate. CMR findings were defined as clinically relevant, if resulting in a new diagnosis, change of treatment or additional diagnostic procedure.

RESULTS

44/76 patients demonstrated pathological CMR findings. In 24/76 patients, the pathology was detected by CMR and not by echocardiography. CMR-based diagnoses of cardiac disease were established in 20/76 patients, and all were morphological substrates for VA. In seven patients, the location of the CMR finding (scar) directly matched the VA origin. CMR findings resulted in a change of treatment in 21 patients and/or additional diagnostics in 8 patients.

CONCLUSION

Undetected cardiac conditions are frequent causes of VA. This is the first study demonstrating the value of CMR for detection of morphological substrate and/or underlying cardiac disorders in VA patients without known cardiac disease.

ADVANCES IN KNOWLEDGE

The high incidence of clinically relevant CMR findings which were not detected during initial diagnostic work-up strongly supports the use of CMR to screen VA patients for underlying heart disease.

[Cardiac sinus node dysfunction due to a new mutation of the SCN5A gene]

A 10-year-old child was hospitalized for bradycardia during a viral infection with chikungunya. His history showed unexplored episodes of bradycardia. Cardiologic explorations revealed cardiac sinus node dysfunction (SD). Mutational screening of the SCN5A gene showed that this case was a compound heterozygote for p.Ala735Val and p.Asp1792Asn missense mutants. Five years later, the child underwent a pacemaker insertion after an electrophysiological study performed during an atrial flutter access.

Declining into failure: the age-dependent loss of the L-type calcium channel within the sinoatrial node

BACKGROUND

The spontaneous activity of pacemaker cells in the sinoatrial (SA) node controls heart rate under normal physiological conditions. Clinical studies have shown the incidence of SA node dysfunction increases with age and occurs with peak prevalence in the elderly population. The present study investigated whether aging affected the expression of Ca(v)1.2 channels and whether these changes could affect pacemaker activity, in turn leading to age-related SA node degeneration.

METHODS AND RESULTS

The SA node region was isolated from the right atrium of guinea pigs between birth and 38 months of age. Immunofluorescence studies showed Ca(v)1.2 protein was present as punctate labeling around the outer membrane of atrial cells but was absent from the center of the SA node. The area lacking Ca(v)1.2-labeled protein progressively increased from 2.06+/-0.1 (mean+/-SEM) mm2 at 1 month to 18.72+/-2.2 mm2 at 38 months (P<0.001). Western blot provided verification that Ca(v)1.2 protein expression within the SA node declined during aging. Functional measurements showed an increased sensitivity to the L-type calcium blocker nifedipine; SA node preparations stopped beating in 100 micromol/L nifedipine at 1 day old, compared with 30 micromol/L at 1 month and 10 micromol/L at 38 months of age. Furthermore, the amplitude of extracellular potentials declined within the center and periphery of the SA node during aging.

CONCLUSIONS

The present data show Ca(v)1.2 channel protein decreases concurrently with reduced spontaneous activity of the SA node with increased age, which provides further evidence of mechanisms underlying the age-related deterioration of the cardiac pacemaker.

Relevance of inflammatory cell infiltrates for complete atrioventricular block in experimental murine myocarditis

BACKGROUND

There are few systemic pathologic studies on myocarditis. This study aimed to clarify the pathologic characteristics of murine myocarditis.

METHODS

We recorded serial electrocardiograms in experimental viral myocarditis in mice and then examined their cardiac pathology. After taking baseline electrocardiograms, we inoculated the mice intraperitoneally with the encephalomyocarditis virus. Electrocardiograms were serially recorded until 220 days after the virus inoculation.

RESULTS

Serial electrocardiograms revealed ectopic beats, low voltage of the QRS complex, and the appearance of complete atrioventricular (AV) block. Corresponding myocardial lesions were found in the hearts of mice with these ectopic beats. Mononuclear cell infiltrations into the His bundle were most frequently found in mice with complete AV block.

CONCLUSIONS

Inflammatory change with cellular infiltrations was the most common pathologic finding in mice with complete AV block. In clinical settings, anti-inflammatory therapy might be recommended for patients with myocarditis complicated with conduction disturbances.

Complete atrioventricular block in experimental murine myocarditis

BACKGROUND

There were few reports on the pathological characteristics of the conduction system in myocarditis. This study was aimed to clarify the pathological characteristics of complete atrioventricular (AV) block in myocarditis.

METHODS AND RESULTS

We studied serial electrocardiograms in experimental myocarditis in mice and also examined their cardiac pathology. After taking baseline electrocardiograms, mice were inoculated intraperitoneally with the encephalomyocarditis virus. Electrocardiograms were serially recorded until day 360. Serial electrocardiograms revealed the appearance of complete AV block. Myocardial lesions were found in the hearts of mice with these ectopic beats. Mononuclear cell infiltrations into the His bundle and necrotic lesions of the conduction system were found in 10.7% (18/168) of mice with complete AV block. However, 17.3% (29/168) of mice showed no evident pathological lesions except the edematous changes of AV node.

CONCLUSIONS

The appearance of complete AV block in myocarditis may suggest not only significantly comparable pathological lesions of the conduction system but also the trivial edematous changes; in clinical settings, in the former case, permanent pacing therapy is necessary, and in the latter case, the disease may be transient and could be recovered from complete AV block. This study may shed light on the pathological characteristics of complete AV block in myocarditis.

Recurrence of myocarditis presenting as pacing and sensing failure after implantation of a permanent pacemaker at first onset

A 31-year-old woman was admitted to hospital with loss of consciousness and generalized convulsions. Electrocardiography (ECG) showed complete atrioventricular block (AV block) with a pulse rate of 30 beats/min. Endomyocardial biopsy from the right ventricle showed massive necrosis and degeneration of myocardial cells with extensive infiltration of lymphocytes into the interstitial space. These pathological findings suggested fulminant myocarditis. Following glucocorticoid therapy, the patient became asymptomatic, but the AV block did not resolve completely and a bifocal pacemaker was implanted. However, similar symptoms recurred 7 years later. An ECG showed pacing and sensing failure linked to an increase in the pacing threshold and a decrease in the sensing threshold. Endomyocardial biopsy from the right ventricle again showed interstitial infiltration with lymphocytes and eosinophils. After glucocorticoid therapy, she became asymptomatic once more, and the improvement in the pacing and sensing failure, and cardiomegaly, was satisfactory. This patient represents a very rare case of recurrence of acute myocarditis without progression, as much as 7 years after its first occurrence. Glucocorticoid therapy was still effective in treating the recurrent myocarditis presenting with pacing and sensing failure.

Recovery from complete atrioventricular block caused by idiopathic giant cell myocarditis after corticosteroid therapy

Giant cell myocarditis (GCM) is a rapidly progressive disease that leads to ventricular tachycardia or high-grade atrioventricular (A-V) block, frequently requiring a pacemaker. A 64-year-old woman developed syncope as a result of idiopathic GCM with A-V block. She required both a temporary and a permanent pacemaker. Two-dimensional echocardiography showed severely reduced wall motion. There was no histologic or clinical evidence to suggest sarcoidosis. Despite treatment with diuretics and an angiotensin-converting enzyme inhibitor, exertional dyspnea persisted. She received prednisolone 4 months after the onset of complete A-V block in the late phase of GCM. Prednisolone improved A-V nodal conduction in spite of the fact that there was no influence from LV wall motion, and sinus rhythm has continued for more than 2 years. In this patient, prednisolone was effective in the treatment of GCM.

Eosinophilic myocarditis associated with toxicodermia caused by phenobarbital

We report on a 37-year-old man with congestive heart failure caused by eosinophilic myocarditis associated with toxicodermia. He developed many annular skin eruptions and peripheral eosinophilia due to reactions against phenobarbital. Right ventricular endomyocardial biopsy revealed extensive infiltration of eosinophils in the myocardium. A drug lymphocyte-stimulating test (DLST) for phenobarbital was positive. His symptoms, cardiomegaly, and cardiac function were improved by discontinuing phenobarbital followed by oral administration of prednisolone. We conclude that this eosinophilic myocarditis must have been induced by an allergic reaction to phenobarbital and that long-term eosinophilia contributed to the myocardial injury.

Inapparent myocarditis and sudden death in pediatrics. Diagnosis by immunohistochemical staining

We analyzed the anatomopathological findings in two cases of sudden death related to myocarditis in pediatric patients. Since the diagnosis of myocarditis depends either upon histologic and histochemical techniques or the manner the sample was obtained, we describe a more specific immunohistochemical method to stain samples and more accurately diagnose and qualify cellular lymphoid strains in the inflammatory reaction of the myocardium thus allowing a correct diagnosis of myocarditis.

Intraventricular conduction abnormalities in patients with clinically suspected myocarditis are associated with myocardial necrosis

Twenty-nine patients with suspected myocarditis, either with or without intraventricular conduction abnormalities, were investigated for degree of myocardial necrosis by antimyosin scintigraphy. Among those 29 patients, 16 had intraventricular conduction abnormalities. Antimyosin scans were analyzed for heart/lung ratios and semiquantitative visual uptake scores (0 to 4+ scale). Of the 16 patients with conduction abnormalities, 15 (94%) demonstrated visual antimyosin uptake versus 7 (54%) of 13 cases without conduction abnormalities (p < 0.03). In addition, the heart/lung ratios and uptake scores were significantly higher in the group with conduction abnormalities than in the group without (1.64 +/- 0.31 vs 1.39 +/- 0.20, p < 0.03; and 2.3 +/- 0.7 vs 1.4 +/- 0.7, p < 0.005; respectively). In conclusion, intraventricular conduction abnormalities in patients with suspected myocarditis were more strongly associated with active and more severe myocardial necrosis as judged by antimyosin imaging than patients with normal electrocardiograms.