Race and Sex Differences in QRS Interval and Associated Outcome Among Patients with Left Ventricular Systolic Dysfunction.

BACKGROUND: Prolonged QRS duration is associated with increased mortality among heart failure patients, but race or sex differences in QRS duration and associated effect on outcomes are unknown. METHODS AND RESULTS: We investigated QRS duration and morphology among 2463 black and white patients with heart failure and left ventricular ejection fraction ≤35% who underwent coronary angiography and 12-lead electrocardiography at Duke University Hospital from 1995 through 2011. We used multivariable Cox regression models to assess the relationship between QRS duration and all-cause mortality and investigate race-QRS and sex-QRS duration interaction. Median QRS duration was 105 ms (interquartile range [IQR], 92-132) with variation by race and sex (P<0.001). QRS duration was longest in white men (111 ms; IQR, 98-139) followed by white women (108 ms; IQR, 92-140), black men (100 ms; IQR, 91-120), and black women (94 ms; IQR, 86-118). Left bundle branch block was more common in women than men (24% vs 14%) and in white (21%) versus black individuals (12%). In black patients, there was a 16% increase in risk of mortality for every 10 ms increase in QRS duration up to 112 ms (hazard ratio, 1.16; 95% CI, 1.07, 1.25) that was not present among white patients (interaction, P=0.06). CONCLUSIONS: Black individuals with heart failure had a shorter QRS duration and more often had non-left bundle branch block morphology than white patients. Women had left bundle branch block more commonly than men. Among black patients, modest QRS prolongation was associated with increased mortality.

Chagas disease: don't forget it in Latin American patients with heart block!

Chagas disease is caused by the parasite Trypanosoma cruzi, and mostly affects poor rural populations of central and south America. It is mainly acquired by bugs (triatoma) but also by ingestion of the parasite (fresh fruit juices) or by foetal-maternal blood passing. Despite an important decrease in transmission during the last decades in several countries, millions of patients are still chronically infected and most of them are asymptomatic. In 2012-2013, two cases were admitted in our cardiac intensive care unit (ICU) with heart block due to Chagas cardiomyopathy. Diagnosis was established by echocardiography and positive serological results for Trypanosoma cruzi. This report underlines that in cases of heart failure and conduction abnormalities of unclear aetiology, Chagas disease should be taken into consideration, even in patients originating from non-endemic countries.

A young man presenting with paralysis after vigorous exercise.

Thyrotoxic periodic paralysis (TPP) is a rare metabolic disorder characterised by muscular weakness and paralysis in predisposed thyrotoxic patients. Although patients with TPP are almost uniformly men of Asian descent, cases have been reported in Caucasian and other ethnic populations. The rapid increase in ethnic diversity in Western and European nations has led to increase in TPP reports, where it was once considered exceedingly rare. Correcting the hypokalaemic and hyperthyroid state tends to reverse the paralysis. However, failure to recognise the condition may lead to delay in diagnosis and serious consequences including respiratory failure and death. We describe a young man who was diagnosed with hyperthyroidism who presented with acute paralysis. The clinical characteristics, pathophysiology and management of TTP are reviewed.

Mutational spectrum in the Ca(2+)--activated cation channel gene TRPM4 in patients with cardiac conductance disturbances.

Very recently, mutations in the TRPM4 gene have been identified in four pedigrees as the cause of an autosomal dominant form of cardiac conduction disease. To determine the role of TRPM4 gene variations, the relative frequency of TRPM4 mutations and associated phenotypes was assessed in a cohort of 160 unrelated patients with various types of inherited cardiac arrhythmic syndromes. In eight probands with atrioventricular block or right bundle branch block--five familial cases and three sporadic cases--a total of six novel and two published TRPM4 mutations were identified. In patients with sinus node dysfunction, Brugada syndrome, or long-QT syndrome, no mutations were found. The novel mutations include six amino acid substitutions and appeared randomly distributed through predicted TRPM4 protein. In addition, eight polymorphic sites including two in-frame deletions were found. Mutations separated from polymorphisms by absence in control individuals and familial cosegregation in some families. In summary, TRPM4 gene mutations appear to play a major role in cardiac conduction disease but not for other related syndromes so far. The phenotypes are variable and clearly suggestive of additional factors modulating the disease phenotype in some patients.

Prevalence and clinical course of the juveniles with Brugada-type ECG in Japanese population.

BACKGROUND: Although many studies on Brugada syndrome have been done, with many reports of genetic findings and clinical features, little evidence exists to support the role of this syndrome in sudden cardiac death in a juvenile population. We sought to determine the prevalence and clinical course in children exhibiting Brugada-type ECG in a community-based population. METHODS: Our study population comprised 21,944 subjects (11,282 boys and 10,662 girls) who underwent ECG during their first-year elementary school health examinations between 1992 and 2001 in Izumi City, Osaka. Brugada-type ECG was defined as demonstrating ST-segment elevation (coved or saddle-back type, J wave amplitude > or =0.2 mV) in the right precordial leads. We also divided Brugada-type ECGs into three types according to a consensus report. Type 1: coved ST-segment elevation displaying high J wave amplitude followed by a negative T wave; Type 2: high take-off and gradually descending ST-segment elevation (remaining > or =1 mm) followed by a positive or biphasic T wave; and Type 3: ST-segment elevation of <1 mm of both types. RESULTS: Four subjects showed Brugada-type ECG (0.02%) (2 boys and 2 girls). Only one subject, a girl, met Type 1 criteria (0.005%). No history of structural heart disease was documented in these four subjects. During 6.8 +/- 1.0 years of follow-up, no episode of unexpected sudden death, syncopal attack, and fatal arrhythmia occurred. CONCLUSIONS: The prevalence of Brugada-type ECG in a juvenile population was extremely low. To investigate when the typical Brugada-type ECG might be manifested, it could be necessary to check ECGs after adolescence.

Prevalence of the Brugada electrocardiographic pattern at the Medical Center of Louisiana in New Orleans.

Since 1992 the Brugada syndrome has gained recognition as a cause of ventricular fibrillation. The syndrome was originally described in patients with the diagnostic triad of (1) right bundle branch block, (2) an electrocardiogram (ECG) with persistent ST-segment elevation in leads V1, V2, and V3, and (3) sudden cardiac death. Two different types of ST-segment elevation, coved and saddleback, have been described. All patients originally described had structurally normal hearts. The definition of the Brugada electrocardiogram (originally right bundle branch block and ST-segment elevation in V1, V2, and V3 in characteristic coved or saddleback configuration) has been evolving since the initial description, and not all patients with the Brugada electrocardiogram have the Brugada syndrome. We designed a trial to determine the prevalence in our population at the Medical Center of Louisiana in New Orleans of the Brugada ECG as it was originally defined. ECGs performed in 1997 were examined for changes consistent with the Brugada electrocardiogram. Those ECGs with changes secondary to another identifiable cause were excluded. The amount and type of ST-segment elevation in leads V1, V2, and V3 were recorded for the remaining ECGs. From a total of 55,446 electrocardiograms performed on 27,328 patients, we were able to identify only 18 ECGs with the changes originally described by Brugada, and none of them meet current criteria. Our study suggests that in our patient population the ECG now considered typical of the Brugada syndrome is rare.

The Brugada syndrome: a recently recognised genetic disease causing sudden cardiac death.

Australian doctors need to be aware of this little-known syndrome, which is a cause of sudden cardiac death. It is more common among Southeast Asian people, who make up a considerable proportion of our population. We report two cases which represent very different clinical presentations of this condition.

The Brugada syndrome in a Chinese population.

Sudden cardiac death has been reported in patients with a unique electrocardiographic (ECG) abnormality showing right bundle branch block and ST segment elevation in the precordial leads. This syndrome was first described by Brugada and Brugada and has not been previously described in a Chinese population. We report here the first three cases in Singapore. The first patient was a 49-year-old man who presented with syncope, associated with generalized convulsions. The second patient was a 25-year-old man who complained of palpitations but no syncope. The third patient was a 77-year-old man who presented with recurrent episodes of syncope and collapsed with ventricular fibrillation. All patients had no past cardiac or drug history of note. The neurological examination and investigations were normal. All three patients showed a unique right bundle branch block pattern with ST segment elevation in leads V1-3. The echocardiogram and 24-h ambulatory ECG monitoring, were normal. Single vessel disease was present in the third patient. Electrophysiological studies performed in all three patients were able to induce ventricular fibrillation. The patient with resuscitated cardiac death underwent an implantable cardioverter defibrillator implantation. The importance of this syndrome is that the recognition of the unique ECG pattern enables early identification and treatment of these patients.

Hereditary bundle branch defect: right bundle branch blocks of different causes have different morphologic characteristics.

Hereditary bundle branch defect is an autosomal dominant genetic disease that, in a large Lebanese family, was mapped to the long arm of chromosome 19. Affected individuals have various combinations of conduction defects such as right bundle branch block, left or right QRS frontal-axis deviation, or atrioventricular blocks. We now further characterize this disease with the presentation of a two-decade follow-up and analysis of electrocardiographic features and mutation-carrier status. The conduction block may be overt in the first year of life, and among affected individuals, there is a worsening of the conduction block in 5% to 15% of cases, leading to complete atrioventricular block and possibly to sudden death. A group of individuals had QRS anomalies in right precordial leads such as rsr's', rss', or rSr', which may account for partial right bundle branch blocks. In this group, which we referred to as having an "r' pattern," 53% were actually mutation carriers, and 19% evolved toward a complete fascicular block. By contrast, mutation carriers with a normal electrocardiogram remained normal. The QRS morphologic appearance in the right precordial leads of affected individuals and r' pattern mutation carriers is notable for the absence or weakness of negative forces resulting in a rsR' or rR' morphology. In addition, an r' pattern is highly suggestive of a mutation carrier status in the presence of a broad r wave in aVR and s in V6 or a frontal-axis deviation. Finally, mutation carriers demonstrate a conduction block significantly more often in males than females (75% and 50%, respectively). This incomplete penetrance and slow evolution suggest that the actual prevalence of hereditary bundle branch defect is very much underestimated.

Right-branch bundle block in circumpolar Inuit.

The prevalence of right-branch bundle block (RBBB) has been examined in the Inuit residents of Igloolik (69 degrees 40'N, Canadian N.W.T.) over a twenty-year period. Original reports of a very high prevalence of RBBB probably reflected a selective testing of patients with chronic respiratory disease by visiting physicians. Cases of RBBB are certainly seen somewhat more frequently than in a southern community, but the majority of subjects show no more than a slight notching of the R wave of the electrocardiogram, with no appreciable broadening of the QRS complex. While a few of the more marked cases of RBBB may be attributable to chronic respiratory disease, the majority are associated with high normal values for both lung function and predicted maximal oxygen intake. The probable cause is thus a ventricular hypertrophy due to the vigorous physical activity demanded by life in a northern community rather than chronic respiratory disease. The physical demands of life in Igloolik have diminished over the past two decades, and an apparent increase in the prevalence of RBBB over this period is probably due mainly to a great awareness+ of the condition by those reading the electrocardiograms.