Saidi A. Mohiddin

Mutations of MYO6 Are Associated with Recessive Deafness, DFNB37

Cosegregation of profound, congenital deafness with markers on chromosome 6q13 in three Pakistani families defines a new recessive deafness locus, DFNB37. Haplotype analyses reveal a 6-cM linkage region, flanked by markers D6S1282 and D6S1031, that includes the gene encoding unconventional myosin VI. In families with recessively inherited deafness, DFNB37, our sequence analyses of MYO6 reveal a frameshift mutation (36-37insT), a nonsense mutation (R1166X), and a missense mutation (E216V). These mutations, along with a previously published missense allele linked to autosomal dominant progressive hearing loss (DFNA22), provide an allelic spectrum that probes the relationship between myosin VI dysfunction and the resulting phenotype.

Efficacy of implantable cardioverter defibrillator therapy for primary and secondary prevention of sudden cardiac death in hypertrophic cardiomyopathy

Risk stratification and effectiveness of implantable cardioverter‐defibrillator (ICD) therapy are unresolved issues in hypertrophic cardiomyopathy (HCM), a cardiac disease that is associated with arrhythmias and sudden death. We assessed ICD therapy in 132 patients with HCM: age at implantation was 34 ± 17 years , and 44 (33%) patients were aged ≤ 20 years . Indications were sustained ventricular tachycardia (VT) or cardiac arrest (secondary prevention) in 47 (36%) patients, and clinical features associated with increased risk for sudden death (primary prevention) in 85 (64%) patients. There were 6 deaths and 55 appropriate interventions in 27 (20%) patients during a mean follow‐up period of 4.8 ± 4.2 years : 5‐year survival and event‐free rates were 96%± 2% and 75%± 5% , respectively. ICD intervention‐free rates were significantly less for secondary than for primary prevention: 64%± 7% versus 84%± 6% at 5 years, P = 0.02 . Notably, 59 of 67 events (cardiac arrest and therapeutic ICD interventions), or 88%, occurred during sedentary or noncompetitive activity. Incidence of therapeutic shocks was related to age but not to other reported risk factors, including severity of cardiac hypertrophy, nonsustained VT during Holter monitoring, and abnormal blood pressure response to exercise. ICD related complications occurred in 38 (29%) patients, including 60 inappropriate ICD interventions in 30 (23%) patients. However, 8 (27%) of the patients with inappropriate shocks also had therapeutic interventions. ICD is effective for secondary prevention of sudden death in HCM. However, selection of patients for primary prevention of sudden death, and prevention of device related complications require further refinement. (PACE 2003; 26:1887–1896)

Chorein Detection for the Diagnosis of Chorea-Acanthocytosis

Chorea‐acanthocytosis (ChAc) is a severe, neurodegenerative disorder that shares clinical features with Huntingtons disease and McLeod syndrome. It is caused by mutations in VPS13A, which encodes a large protein called chorein. Using antichorein antisera, we found expression of chorein in all human cells analyzed. However, chorein expression was absent or noticeably reduced in ChAc patient cells, but not McLeod syndrome and Huntingtons disease cells. This suggests that loss of chorein expression is a diagnostic feature of ChAc. Ann Neurol 2004;56:299–302

Mutational spectrum of the CHAC gene in patients with chorea-acanthocytosis

Chorea-acanthocytosis (ChAc) is an autosomal recessive neurological disorder whose characteristic features include hyperkinetic movements and abnormal red blood cell morphology. Mutations in the CHAC gene on 9q21 were recently found to cause chorea-acanthocytosis. CHAC encodes a large, novel protein with a yeast homologue implicated in protein sorting. In this study, all 73 exons plus flanking intronic sequence in CHAC were screened for mutations by denaturing high-performance liquid chromatography in 43 probands with ChAc. We identified 57 different mutations, 54 of which have not previously been reported, in 39 probands. The novel mutations comprise 15 nonsense, 22 insertion/deletion, 15 splice-site and two missense mutations and are distributed throughout the CHAC gene. Three mutations were found in multiple families within this or our previous study. The preponderance of mutations that are predicted to cause absence of gene product is consistent with the recessive inheritance of this disease. The high proportion of splice-site mutations found is probably a reflection of the large number of exons that comprise the CHAC gene. The CHAC protein product, chorein, appears to have a certain tolerance to amino-acid substitutions since only two out of nine substitutions described here appear to be pathogenic.

Myocardial bridging does not predict sudden death in children with hypertrophic cardiomyopathy but is associated with more severe cardiac disease

OBJECTIVES We sought to examine the association between systolic compression of sections of epicardial coronary vessels (myocardial bridging) with myocardial perfusion abnormalities and clinical outcome in children with hypertrophic cardiomyopathy (HCM). BACKGROUND It has recently been suggested that myocardial bridging is an important cause of myocardial ischemia and sudden death in children with HCM. METHODS Angiograms from 57 children with HCM were reviewed for the presence of bridging (50% or more maximum systolic arterial compression). QT interval indices, echocardiographic and cardiac catheterization findings, treadmill exercise tests, exercise thallium scintigraphy, Holter monitoring and electrophysiologic study findings were compared in children with and without bridging. The findings were also related to the presence or absence of compression of septal branches of the left anterior descending artery (LAD). RESULTS Bridging was present in 23 (40%) of the children. Multiple coronary arteries were involved in four children. Bridging involved the LAD in 16 of 28 (57%) affected vessels. Myocardial perfusion abnormalities were present in 14 of 30 (47%) children without bridging and in 17 of 22 (94%) children with bridging, p = 0.002. However, bridging was associated with more severe septal hypertrophy (19+/-8 mm vs. 28+/-8 mm, p < 0.001), a higher septum:posterior wall thickness ratio (2.7+/-1.2 vs. 1.8+/-0.9, p < 0.001), and higher left ventricle (LV) outflow gradient (45+/-37 mm Hg vs. 16+/-28 mm Hg, p = 0.002). Compression of septal LAD branches was present in 37 (65%) of the children and was significantly associated with bridging, severity of LV hypertrophy and outflow obstruction. Multivariate analysis demonstrated that LV septal thickness and septal branch compression, and not bridging, were independent predictors of thallium perfusion abnormalities. There was a 90% power at 5% significance to detect an effect of bridging on thallium abnormalities at an odds ratio of 3. Bridging was also not associated with significantly greater symptoms, increased QT and QTc intervals and QTc dispersion, ventricular tachycardia on Holter or induced at EP study, or a worse prognosis. CONCLUSIONS Bridging and compression of septal branches of the LAD are common in HCM children and are related to magnitude of LV hypertrophy. Left ventricular hypertrophy and compression of intramyocardial branches of the epicardial coronary arteries may contribute to myocardial perfusion abnormalities. Our findings suggest that bridging does not result in myocardial ischemia and may not cause arrhythmias or sudden death in HCM children.

Acute myocarditis presenting as acute coronary syndrome: role of early cardiac magnetic resonance in its diagnosis

Background In patients presenting with acute cardiac symptoms, abnormal ECG and raised troponin, myocarditis may be suspected after normal angiography. Aims To analyse cardiac magnetic resonance (CMR) findings in patients with a provisional diagnosis of acute coronary syndrome (ACS) in whom acute myocarditis was subsequently considered more likely. Methods and results 79 patients referred for CMR following an admission with presumed ACS and raised serum troponin in whom no culprit lesion was detected were studied. 13% had unrecognised myocardial infarction and 6% takotsubo cardiomyopathy. The remainder (81%) were diagnosed with myocarditis. Mean age was 45±15 years and 70% were male. Left ventricular ejection fraction (EF) was 58±10%; myocardial oedema was detected in 58%. A myocarditic pattern of late gadolinium enhancement (LGE) was detected in 92%. Abnormalities were detected more frequently in scans performed within 2 weeks of symptom onset: oedema in 81% vs 11% (p<0.0005), and LGE in 100% vs 76% (p<0.005). In 20 patients with both an acute (<2 weeks) and convalescent scan (>3 weeks), oedema decreased from 84% to 39% (p<0.01) and LGE from 5.6 to 3.0 segments (p=0.005). Three patients presented with sustained ventricular tachycardia, another died suddenly 4 days after admission and one resuscitated 7 weeks following presentation. All 5 patients had preserved EF. Conclusions Our study emphasises the importance of access to CMR for heart attack centres. If myocarditis is suspected, CMR scanning should be performed within 14 days. Myocarditis should not be regarded as benign, even when EF is preserved.

Safety and feasibility of hospital discharge 2 days following primary percutaneous intervention for ST-segment elevation myocardial infarction

Aim Primary percutaneous coronary intervention (PPCI) produces more effective coronary reperfusion and allows immediate risk stratification compared with fibrinolysis. We investigated the safety and feasibility of very early discharge at 2 days following PPCI in selected low-risk cases. Methods This was a prospective observational cohort study of 2779 patients who underwent PPCI between 2004 and 2011. Patients meeting the following criteria were deemed suitable for very early discharge; TIMI III flow, left ventricle (LF) ejection fraction >40%, and rhythmic and haemodynamic stability out to 48 h. Higher-risk patients who did not fulfil these criteria were discharged later according to physician preference. All patients were offered outpatient review by a multidisciplinary team. Endpoints included 30 day readmission rates and major adverse cardiac events (MACE) out to a median of 2.8 years (IQR range: 1.3–4.4 years). Results 1309 (49.3%) PPCI patients met very early discharge criteria, of whom 1117 (85.3%) were actually discharged at 2 days. 620 (23.4%) were discharged at 3 days, and 916 (34.5%) >3 days after admission (median 5, IQR: 4–8) days). Patients discharged at 2 days were younger, and had lower rates of diabetes, renal dysfunction, multivessel coronary artery disease, previous myocardial infarction, and previous coronary artery bypass surgery, compared with patients discharged later. 30-day readmission rates for non-MACE events were 4.8%, 4.9% and 4.6% for patients discharged 2 days, 3 days and >3 days after admission, respectively. MACE rates were lowest in patients discharged at 2 days (9.6%, 95% CI 4.7% to 16.6%) compared with patients discharged at 3 days (12.3% 95% CI 6.0% to 19.2%) and >3 days (28.6% 95% CI 22.9% to 34.7%, p<0.0001) after admission. Conclusions Our data suggest that discharge of low-risk patients 2 days after successful PPCI is feasible and safe. Over 40% of all patients with ST-elevation myocardial infarction may be suitable for early discharge with important implications for healthcare costs.

Ventilatory efficiency and resting hemodynamics in hypertrophic cardiomyopathy.

PURPOSE In patients with systolic heart failure, the ability of cardiopulmonary exercise testing (CPX) variables to reflect pathophysiology is well established. The relationship between CPX and pathophysiology has, however, not been thoroughly investigated in patients with nonobstructive hypertrophic cardiomyopathy (NHCM). The objective of this study was to assess the ability of CPX variables to reflect resting hemodynamics in patients with nonobstructive hypertrophic cardiomyopathy NHCM. METHODS We performed CPX and right heart catheterization on 83 subjects with NHCM (51 male/32 female, mean age = 38 +/- 10 yr, NYHA I-III mean = 1.7). Peak oxygen consumption ( O2) and minute ventilation/carbon dioxide ratio (V E/VCO2) at peak exercise were compared to resting hemodynamics including pulmonary artery systolic, diastolic and mean pressures (PASP, PADP and MPAP), and pulmonary capillary wedge pressure (PCWP). RESULTS Elevations in PCWP (> or = 15 mm Hg), PASP (> or =30 and > or = 40 mm Hg), PADP (> 15 mm Hg) and MPAP (> or = 20 mm Hg) were detected in 22, 33, 10, and 23% of subjects, respectively. Peak V E/VCO2 (positive correlation) and peak VO2 (negative correlation) correlated modestly with all pressure measurements (r = 0.33-0.51, P < 0.01 for all measurements). By receiver operating curve analysis, a V E/VCO2 >35.5 exhibited the best diagnostic accuracy with a curve areas of 0.81 for PAP > or = 30 mm Hg (sensitivity/specificity = 86%/67%), 0.87 for PAP > or = 40 mm Hg (77%/100%), 0.86 for MPAP > 20 mm Hg (83%/79%), and 0.84 for PCWP > or = 15 mm Hg (80%/76%). CONCLUSIONS CPX can accurately identify abnormal resting hemodynamics in patients with NHCM. Further testing of this modality in other forms of diastolic dysfunction may be warranted.

Utility of Genetic Screening in Hypertrophic Cardiomyopathy: Prevalence and Significance of Novel and Double (Homozygous and Heterozygous) β-Myosin Mutations

Genetic screening of the beta-myosin heavy chain gene (MYH7) was evaluated in 100 consecutive unrelated patients with hypertrophic cardiomyopathy (HCM) and 200 normal unrelated subjects. Seventeen beta-myosin mutations were identified in 19 patients. Notably, 13, or 76%, were novel. Mutations were detected in both alleles in two patients: homozygous for Lys207Gln in one, and heterozygous for Pro211 Leu and Arg663His in another. No mutation was detected in the controls. MYH7-associated HCM was associated with more marked left atrial enlargement and syncope than non-MYH7-related HCM. Our findings indicate that: (1) screening methods should allow identification of novel mutations; and (2) more than one sarcomeric mutation may be present in a patient more commonly than is appreciated. Further studies are necessary to ascertain the clinical consequences of the novel and compound gene abnormalities, and to determine whether correlating functional domain to phenotype provides more useful information about the clinical significance of the molecular defects.

Diagnosis and management of patients with acute cardiac symptoms, troponin elevation and culprit-free angiograms

Patients with acute cardiac symptoms, elevated cardiac troponin and culprit-free angiograms comprise a significant proportion of patients admitted with presumed acute coronary syndromes (ACS). International guidelines recommend that these patients receive lifelong secondary prevention under the presumption that angiographically undetectable coronary artery disease is the likeliest cause for their presentation. Recent studies using cardiac MRI suggest myocarditis to be the most common cause of these presentations. Emerging data also suggest that myocarditis presenting like an ACS may not be benign. In this article the current literature on patients presenting with acute cardiac symptoms, elevated cardiac troponins but culprit-free angiograms is reviewed, focusing on the diagnostic utility of cardiac MRI in this cohort, and the importance of diagnosing acute myocarditis. The development of higher sensitivity troponin assays will undoubtedly lead to an increase in the number of patients with presumed ACS but culprit free angiography. Robust management pathways including cardiac MRI are vital for cardiac centres dealing with these patients in order to achieve cost-effective, individualised patient care.