Faculty Bibliography

Arrhythmogenic right ventricular dysplasia (ARVD), also known as arrhythmogenic right ventricular cardiomyopathy, is a genetic cause for sudden cardiac arrest. In ARVD, there is progressive replacement of normal myocytes, with fat and fibrous tissue, predominantly in the right ventricle that predisposes the individual to arrhythmias. Patients who are identified with this condition are risk stratified; those at high risk are recommended to have implanted cardioverter defibrillators.

Sudden cardiac death (SCD) in young athletes is generally caused by inherited cardiac disorders. While these events are relatively few compared to other cardiac deaths, they are tragic in that death occurs in a young, otherwise healthy person. The genetic abnormalities most associated with SCD are hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia. As a result of growing awareness that these deaths can be prevented, guidelines have been issued in both Europe and the United States to help screen and determine qualification for young persons who want to participate in competitive athletics. There remains debate on the how extensive screening should be, in particular over the use of the 12-lead electrocardiogram (ECG), with European guidelines mandating ECG and United States guidelines not recommending routine use of the ECG.

Brugada syndrome is a genetic cause of sudden cardiac arrest characterized by abnormal electrocardiographic (ECG) pattern in the right precordial leads either at rest or after provocation. In this condition, sudden death may occur due to polymorphic ventricular tachycardia or ventricular fibrillation. In approximately 30% of patients, sudden cardiac arrest is the initial clinical manifestation of Brugada syndrome. Treatment strategies for Brugada syndrome are evolving. Currently, the implanted cardioverter defibrillator (ICD) is the only proven treatment for Brugada syndrome. Candidates for ICD include patients include those with the type 1 ECG pattern or who have been successfully resuscitated from sudden death or have had unexplained syncope.

Congenital long QT syndrome is a genetic disorder characterized by prolonged QT interval on electrocardiogram and increased risk of sudden cardiac death from ventricular arrhythmias. In long QT syndrome, genes that encode for the various cardiac ion channels or regulatory proteins of these channels are mutated. The various mutations individually lead to a disruption of the normal cardiac myocyte action potential, and thus leading to a propensity for ventricular arrhythmias. Diagnosis can be difficult with patient presentations ranging from palpitations to syncope to sudden cardiac death. The QT interval can also vary over time, often requiring further testing to support the diagnosis. Recently developed genetic testing can be used to identify the responsible genes in patients with known disease. It can also be used to genotype the affected patient's family members. The current test panel only recognizes common mutations resulting in a falsely negative test for those with a rare or unidentified variant. For treatment, beta-blocker therapy is recommended for all patients, and implantable cardioverter-defibrillator (ICD) placement is recommended for those who are at high risk for a cardiac event. Future investigations will concentrate genotype-guided risk stratification for ICD placement and on genotype-specific pharmacological therapy.

BACKGROUND: We analyzed the clinical and quantitative echocardiographic characteristics of patients with sub-basal hypertrophic cardiomyopathy (HCM) to define the characteristics of patients (pts) with severe symptoms. METHODS: Of 444 pts in a referral-based HCM program, 22 (5%) had midventricular or apical HCM. Quality of life (QoL) questionnaire was administered as an independent confirmer of symptomatic state. RESULTS: Ten pts were NYHA III and IV, and 12 pts were NYHA I and II; QoL scores (41 +/- 26 vs. 10 +/- 13, P = 0.001) confirmed a priori division of two groups based on NYHA classification. Pts with more severe symptoms were more likely female (70% vs. 25%, P = 0.001) with atrial fibrillation (40% vs. 0%, P = 0.02). They more frequently had midventricular HCM 60% versus 8% (P = 0.01) (mid-LV thickness 17 +/- 6 vs. 12 +/- 2 mm, P = 0.03) and had much smaller LV diastolic volumes 68 +/- 12 versus 102 +/- 22 ml (39 +/- 4 vs. 53 +/- 12 ml/m(2), P = 0.001). Septal E/E' was higher in the severely symptomatic pts (15 +/- 5 vs. 7 +/- 3, P = 0.001) indicating higher estimated LV filling pressure. Midobstruction with apical akinetic chamber was noted in 4/10 pts who developed refractory symptoms. Cardiac mortality was higher in the severely symptomatic patients, 4/10 who had midventricular HCM as compared to 0/12 in the mildly symptomatic apical HCM group (P = 0.03). CONCLUSIONS: In subbasal HCM, pts with severe symptoms have midventricular hypertrophy, with encroachment of the LV cavity and consequent very small LV volumes that may be complicated by mid-LV obstruction. Pts with mid-LV hypertrophy are more symptomatic than those with apical HCM, are often refractory to therapy, and have higher mortality.

The shape of Doppler velocity tracings in obstructive hypertrophic cardiomyopathy offers insights into its pathophysiology. Inflection points are the points on a curve where its shape changes from concave to convex, or vice versa. These dynamic systolic abnormalities are caused: 1) by the amplifying nature of the obstruction; and 2) by the adverse effect of the sudden imposition of afterload in midsystole. The midsystolic drop in left ventricular ejection velocities and the premature termination of longitudinal shortening are compelling evidence of the deleterious mechanical effect of obstruction on the ventricle. This dynamic systolic dysfunction, demonstrated on the Doppler curves, may contribute to heart failure symptoms and adverse outcome. In outflow obstruction, these abnormalities normalize after abolition of gradient. Therefore, their detection in an individual patient confirms obstruction as a therapeutic target.

AIMS: A transthoracic echocardiographic (TTE) parameter that would stratify atrial fibrillation (AF) risk would be useful. Tissue Doppler imaging can quantify left atrial appendage contraction velocity (LAA A(M)). METHODS AND RESULTS: We studied 141 patients referred for transoesophageal echocardiogram (TEE); 48 were in AF. We obtained TEE and TTE LAA A(M) velocities from the LAA apex on the parasternal short-axis and apical two-chamber views. Adequate traces were obtained in 118 patients (84%). In these patients, we measured 5382 LAA A(M) velocity tracings. There was a strong correlation between LAA A(M) on TEE and TTE parasternal short-axis (r = 0.741; P < 0.0001) and apical two-chamber views (r = 0.729; P < 0.0001). Patients in AF had lower LAA A(M) than those with sinus rhythm on parasternal short-axis (12 +/- 5 vs. 23 +/- 7 cm/s, P < 0.0001) and apical two-chamber (14 +/- 5 vs. 23 +/- 8 cm/s, P < 0.0001) views. On parasternal short axis, LAA A(M) velocities were lower in patients with spontaneous echo contrast, 11 +/- 4 vs. 22 +/- 8 cm/s (P < 0.0001), and in those with thrombus, 8 +/- 2 cm/s (P < 0.0001). On apical two-chamber, LAA A(M) velocities were also lower with spontaneous echo contrast, 12 +/- 4 vs. 22 +/- 7 cm/s (P < 0.0001), and with thrombus, 10 +/- 4 cm/s (P < 0.0001). In patients with AF and TTE LAA A(M) < or =11 cm/s, we found that nearly one-third had LAA thrombus. In patients with AF and a history of stroke or transient ischaemic attack (TIA), LAA A(M) velocities were lower compared with those without history of stroke or TIA in the parasternal short-axis (9 +/- 3 vs. 13 +/- 5 cm/s, P = 0.02) and apical two-chamber views (11 +/- 3 vs. 15 +/- 6 cm/s, P = 0.008). CONCLUSION: Acquiring and quantifying LAA A(M) contraction velocity is feasible on TTE in a high percentage of patients and correlates with TEE. LAA A(M) was lower in AF compared with sinus rhythm, with spontaneous echo contrast compared to without spontaneous echo contrast, and in AF patients with a history of stroke or TIA. Those with LAA thrombus had the lowest LAA A(M) velocities. LAA A(M) is a novel functional parameter that may prove useful for risk stratification of AF

It is now 50 years since the modern description of hypertrophic cardiomyopathy (HCM). The initial descriptions foretold the current efforts towards sudden death prevention, alleviation of heart failure symptoms and angina, relief of left ventricular outflow tract obstruction, preparticipation athletic screening, family screening and genetic testing. The authors review the salient features of HCM, focusing on therapeutic strategies to manage its symptoms and attempts to prevent sudden death.

BACKGROUND: Abnormal positioning and size of the mitral valve contribute to the systolic anterior motion and mitral-septal contact that are important components of obstructive hypertrophic cardiomyopathy (HCM). The RPR repair (resection of the septum, plication of the anterior leaflet, and release of papillary muscle attachments) addresses all aspects of this complex pathology. This study reports outcomes regarding effectiveness of the RPR repair. METHODS: Fifty consecutive unselected patients (average age, 55.8 years) undergoing RPR repair for obstructive HCM from 1997 to 2007 were studied. Each patient underwent preoperative and postoperative transthoracic echocardiograms to document gradient, ejection fraction, degree of mitral regurgitation, and systolic anterior motion. Intraoperative transesophageal echocardiogram was used to guide all surgical repairs. Clinical follow-up included patient interviews to determine New York Heart Association (NYHA) status. RESULTS: Concomitant operations were performed in 25 patients (50%). Postoperative mortality was 0%. Average mean left ventricular outflow tract gradients decreased from 134 +/- 40 to 2.8 +/- 8.0. Mitral regurgitation improved from a mean of 2.5 to 0.1 (p < 0.001). Average length of stay was 6.9 +/- 2.7 days. NYHA class improved from 3.0 +/- 0.6 to 1.2 +/- 0.5. Follow-up was 100%, with a mean of 2.5 +/- 1.8 years. Average mitral regurgitation at follow-up was 0.9, with no residual systolic anterior motion. CONCLUSIONS: The RPR repair is safe and effective for symptomatic obstructive HCM. Our data support repair of the mitral valve that results in good intermediate outcomes with respect to gradient, mitral regurgitation, and clinical status.