Sunil T. Mathew

Quantitative breath-hold monitoring of myocardial gadolinium enhancement using inversion recovery trueFISP

The purpose of this work was to develop and evaluate the accuracy of a breath‐hold IR‐TrueFISP acquisition capable of monitoring gadolinium (Gd) concentrations through T1 measurements in the left ventricular blood pool and segments of the myocardium over an extended duration. Measurements using a phantom were performed to assess the accuracy of the technique. Accurate T1 measurements in the expected range after contrast agent administration were obtained with several theoretical formulations. Accurate T1 values before the administration of the contrast agent were obtained only when the incomplete recovery of magnetization during the delay time (TD) between imaging segments was incorporated into the observed signal intensity calculations. T1 measurements over a 1‐hr time period were performed in four subjects with known myocardial infarctions. In this small study, Gd differences between recent and old myocardial infarctions were observed. Magn Reson Med 53:367–371, 2005.

Resynchronization therapy for heart failure

AbstractThis review article discusses the role of resynchronization therapy pacing in the treatment of drug-refractory heart failure. The pathophysiological mechanisms underlying heart failure are first examined including the mechanical and electrical implications of a decrement in the cardiac contractile state. Next, the concept of atrial synchronized biventricular pacing and its effect of maintaining ventricular activation sequences near normalcy are discussed. Clinical evidence is cited concerning the hemodynamic improvement achieved by this mode of pacing. The placement of a lead to attain optimal left ventricular stimulation remains a challenging process and is still evolving as new pacemaker lead designs are being formulated. Overall, biventricular pacing seems to be a promising adjuvant treatment modality for severe heart failure; its true impact will become manifest as more patients receive resynchronization therapy.

1094 Normal left ventricular structure and function: inflection point in age effects

Results Women had higher EF and lower EDVi, ESVi and LVMi compared to men. With increasing age, systolic blood pressure increased, EDVi and ESVi decreased, EF increased, LVMi did not show a clear trend and LVMi/ EDVi increased. However, there was an inflection point at age 50, with EDVi, ESVi and systolic blood pressure for each decade >50 differing significantly from all decades <50 but no differences among decades <50 or >50 years. (Table 1.) Conclusion Age and blood pressure related concentric remodeling results in reduced chamber volumes and increased EF in presence of constant LV mass in both men and women. There is an inflection point at age 50 when chamber volumes fall and blood pressure increases in both genders. Further studies are needed to determine the physiologic basis of changes occurring in LV structure and function at age 50. from 11th Annual SCMR Scientific Sessions Los Angeles, CA, USA. 1–3 February 2008

Cor triatriatum sinistrum

AbstractCor triatriatum sinistrum (CTs) represents approximately 0.1% of congenital heart disease. The presence of an abnormal, often fenestrated fibromuscular membrane is indicative of CTs and results in a subdivided left atrium that can obstruct pulmonary venous return leading to elevated pulmonary venous and pulmonary artery pressures. We describe a case of CTs presenting well into adulthood with the unusual association of atrial flutter. Given the rarity of CTs, this unique observation with atrial flutter is limited to this case report, but is meant to illustrate the ramifications of this arrhythmia even in this relatively simple congenital heart defect, as our patients arrhythmia was refractory to treatment and behaved similarly to atrial flutter observed among patients with more complex heart defects. Accurate diagnosis of the abnormal atrial membrane in the setting of other cardiac defects is imperative because pulmonary venous obstruction can occur after surgery for the associated defects. An ass...

T-wave alternans, a potential non-invasive marker for ventricular arrhythmias.

The leading cause of cardiac-related mortality in the United States is sudden cardiac death (SCD)1. The incidence of SCD (often preceded by ventricular tachyarrhythmias) is one to two individuals per thousand annually2. Clinical trials such as the Multicenter Automatic Defibrillator Implantation Trial (MADIT) and the Antiarrhythmics Versus Implantable Defibrillators (AVID) have demonstrated that there are effective treatment options to reduce SCD. However, the ability to accurately stratify∞∞patients at risk for SCD remains limited. Most∞∞patients referred for treatment are usually survivors of cardiac arrest or sustained ventricular tachyarrhythmias. This referred∞∞patient population is estimated to comprise only about 3% of those∞∞patients who ultimately succumb to SCD3. Identification and risk stratification of the population “not referred” for prevention of SCD also remains a challenge. Current noninvasive diagnostic test(s) are limited. Screening tests employed for evaluating the risk of SCD include the following: left ventricular ejection fraction (LVEF)4,5; 24-hour Holter monitoring for identification of frequent and/or complex ventricular ectopy6; signal-averaged electrocardiography (SAECG)7,8; measures of autonomic tone reflected by heart rate variability and baroreflex sensitivity9-11; QT dispersion (QTd)12. Effective risk stratification has not been achieved with these noninvasive tests since they have inadequate sensitivity and specificity13. Furthermore, the majority of∞∞patients once identified with a positive test never develop malignant ventricular tachyarrhythmias14. For example, Holter monitoring has the ability to document potential malignant arrhythmias. However, less than 10% of post-infarction∞ patients with tachyarrhythmias during Holter monitoring had SCD thereby indicating this test’s poor predictive value15. The role of QTd as a marker for SCD is similarly controversial15. QT-dispersion (QTd), defined as the interlead difference of the QT-interval on the surface ECG16,17, has been hypothesized to reflect regional differences in repolarization of the myocardium that may lead to fibrillation18,19. Other investigators have suggested that QTd simply reflects the vectors of repolarization and may not have significant prognostic value15. Although some studies suggest that QTd may be useful as a risk marker for SCD, other studies have generated conflicting results15. Because of these inconsistencies, QTd has not been utilized as an effective marker for future arrhythmic events15. LVEF has been a relevant predictor of cardiac mortality rate20. Multiple studies examining post-infarction∞∞patients with LVEF less than 40% have revealed that this population was 1.6 times more likely to have ventricular tachycardia than those exhibiting an LVEF more than 40%21. If all∞∞patients with LVEF less than 40% are considered at risk for SCD, LVEF will have a high sensitivity. However, its specificity will be quite low since the total mortality rate in∞∞patients with LVEF less than 40% is low15. If a cutoff rate of 20% is used, the specificity increases but the sensitivity decreases as a significant proportion of∞∞patients with LVEF of 20-40% is missed15. Studies estimate the sensitivity of LVEF to be between 40-75%. Furthermore, the utility value in using LVEF as a measure of risk stratification is that it carries a positive predictive value of only about 16%22. Heart rate variability (HRV) and baroreflex sensitivity (BRS) are noninvasive tests used to estimate function of the autonomic nervous system. HRV is mainly influenced by the balance of the sympathetic and Address for correspondence: Sunil T. Mathew, M.D., 43-41 162nd St., Apt. 1A, Flushing, NY 11358 USA, E-mail: stmathew@excite.com