Risk stratification and subclinical phenotyping of dilated and/or arrhythmogenic cardiomyopathy mutation-positive relatives: CVON eDETECT consortium.

In relatives of index patients with dilated cardiomyopathy and arrhythmogenic cardiomyopathy, early detection of disease onset is essential to prevent sudden cardiac death and facilitate early treatment of heart failure. However, the optimal screening interval and combination of diagnostic techniques are unknown. The clinical course of disease in index patients and their relatives is variable due to incomplete and age-dependent penetrance. Several biomarkers, electrocardiographic and imaging (echocardiographic deformation imaging and cardiac magnetic resonance imaging) techniques are promising non-invasive methods for detection of subclinical cardiomyopathy. However, these techniques need optimisation and integration into clinical practice. Furthermore, determining the optimal interval and intensity of cascade screening may require a personalised approach. To address this, the CVON-eDETECT (early detection of disease in cardiomyopathy mutation carriers) consortium aims to integrate electronic health record data from long-term follow-up, diagnostic data sets, tissue and plasma samples in a multidisciplinary biobank environment to provide personalised risk stratification for heart failure and sudden cardiac death. Adequate risk stratification may lead to personalised screening, treatment and optimal timing of implantable cardioverter defibrillator implantation. In this article, we describe non-invasive diagnostic techniques used for detection of subclinical disease in relatives of index patients with dilated cardiomyopathy and arrhythmogenic cardiomyopathy.

The cardiac sodium channel displays differential distribution in the conduction system and transmural heterogeneity in the murine ventricular myocardium.

Cardiac sodium channels are responsible for conduction in the normal and diseased heart. We aimed to investigate regional and transmural distribution of sodium channel expression and function in the myocardium. Sodium channel Scn5a mRNA and Na(v)1.5 protein distribution was investigated in adult and embryonic mouse heart through immunohistochemistry and in situ hybridization. Functional sodium channel availability in subepicardial and subendocardial myocytes was assessed using patch-clamp technique. Adult and embryonic (ED14.5) mouse heart sections showed low expression of Na(v)1.5 in the HCN4-positive sinoatrial and atrioventricular nodes. In contrast, high expression levels of Na(v)1.5 were observed in the HCN4-positive and Cx43-negative AV or His bundle, bundle branches and Purkinje fibers. In both ventricles, a transmural gradient was observed, with a low Na(v)1.5 labeling intensity in the subepicardium as compared to the subendocardium. Similar Scn5a mRNA expression patterns were observed on in situ hybridization of embryonic and adult tissue. Maximal action potential upstroke velocity was significantly lower in subepicardial myocytes (mean +/- SEM 309 +/- 32 V/s; n = 14) compared to subendocardial myocytes (394 +/- 32 V/s; n = 11; P < 0.05), indicating decreased sodium channel availability in subepicardium compared to subendocardium. Scn5a and Na(v)1.5 show heterogeneous distribution patterns within the cardiac conduction system and across the ventricular wall. This differential distribution of the cardiac sodium channel may have profound consequences for conduction disease phenotypes and arrhythmogenesis in the setting of sodium channel disease.

K(ATP) channel opening during ischemia: effects on myocardial noradrenaline release and ventricular arrhythmias.

Cardioprotection by K(ATP) channel openers during ischemia is well documented although ill understood. Proarrhythmic effects may be an important drawback. K(ATP) channel modulation influences neurotransmitter release during ischemia in brain synaptosomes. Therefore, we studied the effects of K(ATP) channel modulation on myocardial noradrenaline release and arrhythmias in ischemic rabbit hearts. Isolated rabbit hearts were perfused according to Langendorff and stimulated. Local electrograms were recorded and K+-selective electrodes were inserted in the left ventricular free wall. Cromakalim (3 microM) or glibenclamide (3 microM) was added 20 min prior to induction of global ischemia. After 15, 20, or 30 min of ischemia, hearts were reperfused and noradrenaline content of the first 100 ml of reperfusate was measured. Cromakalim (n = 16) prevented the second rise of extracellular [K(+)] in accordance with its cardioprotective effect. Cromakalim significantly reduced noradrenaline release after 15 min (mean, 169 +/- SEM 97 pmol/gr dry weight vs. control 941 +/- 278; p < 0.05) and 20 min of ischemia (230 +/- 125 pmol/gr dry wt vs. control 1,460 +/- 433; p < 0.05), but after 30 min of ischemia, the difference in noradrenaline release was no longer significant (cromakalim 2,703 +/- 1,195 pmol/gr dry wt vs. control 5,413 +/- 1,310; p = 0.08). Ventricular fibrillation or ventricular tachycardia occurred in 10 of 13 control hearts (77%) (n = 19), in six of 10 glibenclamide-treated hearts (60%) (n = 15), and in six of 14 cromakalim-treated hearts (43%) (p = NS). Cromakalim significantly accelerated onset of ventricular tachycardia or fibrillation (mean +/- SEM onset after 12.5 +/- 1.6 min ischemia vs. control 16.2 +/- 0.7 min; p < 0.05). Noradrenaline release occurred only in cromakalim-treated hearts with early-onset arrhythmias whereas no noradrenaline release was observed in cromakalim-treated hearts without ventricular tachycardia or fibrillation. Our results show that activation of the K(ATP) channel by cromakalim during ischemia reduces myocardial noradrenaline release and postpones the onset of irreversible damage, contributing to the cardioprotective potential of K(ATP) openers during myocardial ischemia.

Late ventricular arrhythmias during acute regional ischemia in the isolated blood perfused pig heart. Role of electrical cellular coupling.

OBJECTIVE: Acute ischemia comes with two phases of life-threatening arrhythmias, early (within 10 minutes, 1A) and late (after about 15 minutes, 1B). The mechanism of the latter is unknown and in this paper, we test the hypothesis that a phase of intermediate coupling between surviving epicardium and inexcitable midmyocardium underlies 1B arrhythmias. METHODS: Pig hearts (n=26) were retrogradely perfused with a blood Tyrode's mixture. The left anterior descending artery was occluded. We investigated (1) inducibility of ventricular fibrillation (VF) with programmed stimulation, (2) tissue impedance (Rt) heterogeneity within the ischemic zone, (3) multiple subepicardial and midmyocardial electrograms, (4) subepicardial lactate dehydrogenase (LDH) and glycogen content. RESULTS: In nine of ten hearts, one--three premature stimuli caused VF between 14 and 53 min of ischemia. This typically happened when the Rt of the ischemic zone had increased up to 40% of its final value. More uncoupling terminated the period of VF inducibility. The excitability of the surviving subepicardial layer was depressed during the same period with partial uncoupling, but recovered when the uncoupling from the midmyocardium had progressed further. CONCLUSIONS: We show that 1B-VF can be induced within a distinct time window and coincides with a distinct range of Rt rise. Subepicardium is electrically depressed, presumably through coupling with midmyocardium, complete uncoupling causes subepicardial recovery and terminates the substrate for 1B-VF. Hence, we suggest that the substrate for 1B-VF consists of intermediate coupling of subepicardium and midmyocardium.

Diagnosis and long-term follow-up of the Brugada syndrome in patients with idiopathic ventricular fibrillation.

AIMS: Some patients with idiopathic ventricular fibrillation may suffer from the Brugada syndrome. The diagnostic criteria for the Brugada syndrome are uncertain and arbitrarily set. Therefore, we studied the prevalence of the Brugada syndrome using various diagnostic criteria and long-term follow-up in 37 idiopathic ventricular fibrillation patients. METHODS AND RESULTS: Idiopathic ventricular fibrillation was diagnosed after thorough clinical evaluation in 37 survivors of an out-of-hospital cardiac arrest referred to our institute (UMC Utrecht). Retrospectively, nine patients (24%, group I) were classified as potentially having the Brugada syndrome based on the presence of (in)complete right bundle branch block and ST-segment elevation in leads V(1)-V(3)of > or =1 mm. Only three patients (8%, group II) showed (in)complete right bundle branch block and > or =2 mm ST-segment elevation. With the intermittent presence of these ECG features and/or their (re)appearance with class I antiarrhythmic drugs included as criteria, the percentage of the Brugada syndrome was attenuated in group I (2/37; 5%) and group II (1/37; 3%). Sixteen (43%) of all idiopathic ventricular fibrillation patients (mean follow-up 77+/-41 months) had a recurrent episode of syncope, ventricular tachyarrhythmias or sudden death. Recurrence rate was 3/9 (33%) in Brugada patients group I, 2/3 (66%) in group II and 13/28 (46%) in patients without the Brugada syndrome (P=ns). CONCLUSIONS: Depending on the diagnostic criteria used, the Brugada syndrome was observed in 3% to 24% of patients with idiopathic ventricular fibrillation, underlining the importance of defining the precise diagnostic criteria in these patients. For all idiopathic ventricular fibrillation patients, the ventricular tachyarrhythmia recurrence rate was substantial during an average follow-up of more than 6 years.

Prediction of progression of radiologic damage in newly diagnosed rheumatoid arthritis.

OBJECTIVE: To investigate the extent to which early radiologic damage is predicted by joint inflammation in patients with newly diagnosed rheumatoid arthritis (RA). METHODS: Regression analysis was performed on 1-year progression of total radiologic damage for baseline characteristics and cumulative disease activity measures, and the effects of continued joint inflammation on the progression of damage in separate joint groups were investigated. RESULTS: Odds ratios for progression of total damage were 12 for the presence of rheumatoid factor, 5 for the presence of damage at baseline, and 2 for cumulative joint inflammation. A positive association between continued joint inflammation and progression of damage was found to be statistically significant for most joint groups. CONCLUSION: Progression of radiologic damage in patients with newly diagnosed RA is independently associated with the presence of rheumatoid factor and damage at baseline and with cumulative joint inflammation.