Transesophageal echocardiography: State-of-the art and future directions

Transesophageal echocardiography complements transthoracic examination in 5–10% of patients referred to the echocardiographic laboratory. Clinical indications for performing this procedure are continually evolving. The semi-invasive nature of this procedure necessitates that it be judiciously used and that trained personnel undertake the procedure. Complications of the procedure need to be kept in mind. Future directions in the development of this technology involve newer, muttiplanar, muttifrequency transducers, digital archiving and retrieval, wide-field imaging, and 3-dimensional reconstruction. For the present, transthoracic echocardiography must remain the primary echocardiographic window imaging the heart, with defined clinical applications for transesophageal echocardiography.     

Prognostic significance of impairment of heart rate response to exercise: impact of left ventricular function and myocardial ischemia

OBJECTIVES: The goal of this research was to study the association between heart rate (HR) response to exercise and the risk of death and myocardial infarction (MI) after adjustment for left ventricular (LV) function and myocardial ischemia. BACKGROUND: Chronotropic incompetence during exercise testing is associated with increased mortality. It is unknown whether LV dysfunction or ischemia accounts for this. METHODS: We studied 3,221 patients (age 59 +/- 12 years; 1,701 men) who underwent treadmill exercise echocardiography. We considered two markers of chronotropic incompetence: 1) failure to achieve 85% of the maximal predicted HR, and 2) low (<0.8) chronotropic index. The independent association between HR response and end points was evaluated by an adjusted risk (AR) model, which included clinical parameters, ejection fraction, and the severity of ischemic wall motion abnormalities. RESULTS: Target HR was not achieved in 495 (15%) patients. Low chronotropic index was observed in 793 (25%) patients. There were 129 deaths (41 cardiac) during a median follow-up of 3.2 years. Myocardial infarction occurred in 65 patients. Low chronotropic index was associated with cardiac death (AR, 1.54; 95% confidence interval [CI], 1.18 to 2.04; p = 0.002) and MI (AR, 1.37; 95% CI, 1.09 to 1.69; p = 0.007). Failure to achieve 85% of maximal predicted HR was associated with increased mortality (AR, 1.49; 95% CI, 1.02 to 2.22; p = 0.04) and cardiac death (AR, 2.13; 95% CI, 1.10 to 4.17; p = 0.03). CONCLUSIONS: Impaired chronotropic response to exercise is associated with increased mortality and cardiac events even after adjusting for LV function and the severity of exercise-induced myocardial ischemia.     

Prediction of mortality in patients with left ventricular hypertrophy by clinical,exercise stress,and echocardiographic data

OBJECTIVES: This study evaluated the clinical, exercise stress test, and echocardiographic predictors of mortality and cardiac events in patients with left ventricular hypertrophy (LVH). BACKGROUND: Left ventricular hypertrophy is associated with an increased risk of cardiovascular morbidity and mortality. METHODS: Symptom-limited treadmill exercise echocardiography was performed for evaluation of coronary artery disease in 483 patients (age, 66 +/- 11 years; 281 men) with LVH. End points during follow-up were all-cause mortality and hard cardiac events (cardiac death and nonfatal myocardial infarction [MI]). RESULTS: Forty-six patients died and 14 had nonfatal MI. The cumulative mortality rate was higher in patients with abnormal exercise echocardiography (3% vs. 0.4% at one year, 11.7% vs. 3.7% at three years, and 18.3% vs. 9.5% at five years, p < 0.001). In a sequential multivariate analysis model of clinical, exercise test, and rest and exercise echocardiographic data, incremental predictors of mortality were workload (hazard ratio [HR], 0.5; 95% confidence interval [CI], 0.3 to 0.9), rate pressure product (HR, 0.7; 95% CI, 0.5 to 0.9), left ventricular (LV) mass index (HR, 1.4; 95% CI, 1.1 to 1.8), and failure to increase ejection fraction (EF) with exercise (HR, 2.1; 95% CI, 1.1 to 3.8). Predictors of cardiac events were history of coronary artery bypass grafting (HR, 2.6; 95% CI, 1.2 to 5.4), lower exercise rate-pressure product (HR, 0.6; 95% CI, 0.5 to 0.8), resting wall motion score index (HR, 1.4; 95% CI, 1.1 to 1.8), and failure to increase EF with exercise (HR, 3.3; 95% CI, 1.6 to 6.9). CONCLUSIONS: In patients with LVH, LV mass index and EF response to exercise are independent predictors of mortality, incremental to clinical and exercise test data and resting LV function. A normal exercise echocardiogram predicts a relatively low mortality rate during the following three years.     

Relation of coronary artery disease and cerebrovascular disease with atherosclerosis of the thoracic aorta in the general population.

The association between clinical coronary artery disease, cerebrovascular disease, and aortic atherosclerosis has not been examined in the general population. Transesophageal echocardiography was performed in 581 subjects, a random sample of the Olmsted County (Minnesota) population aged >/=45 years, participating in the Stroke Prevention: Assessment of Risk in a Community (SPARC) study. The frequency and severity of atherosclerosis of the thoracic aorta were determined in the population and the association between clinical coronary artery disease, cerebrovascular disease, and aortic atherosclerosis was examined. Previous myocardial infarction, angina pectoris, and coronary artery bypass surgery were significantly associated with aortic atherosclerosis, adjusting for age and gender (p 4-mm thick, ulcerated plaques, or mobile debris), adjusting for age and gender (p <0.05). Age, smoking, pulse pressure, previous myocardial infarction (odds ratio [OR] 4.67; 95% confidence interval [CI] 1.42 to 15.40), and coronary artery bypass surgery (OR 5.12; 95% CI 1.01 to 26.01) were independently associated with aortic atherosclerosis. Among subjects with atherosclerosis, age, smoking, pulse pressure, hypertension treatment, and coronary artery disease (OR 2.50; 95% CI 1.18 to 5.30) were independently associated with complex atherosclerosis. Weak associations were observed between previous ischemic stroke, transient ischemic attack, and aortic atherosclerosis, associations that were not significant after age- and gender-adjustment (p >0.2). Thus, coronary artery disease is strongly associated with aortic atherosclerosis and complex atherosclerosis in the general population. Cerebrovascular disease is weakly associated with aortic atherosclerosis, thereby questioning the overall importance of aortic atherosclerosis in the pathogenesis of cerebrovascular events in the general population.     

Role of echocardiography in the diagnosis and management of asymptomatic severe aortic stenosis

Calcification of normal tricuspid and congenital bicuspid valves is the most common cause of aortic stenosis in industrialized countries. There is compelling evidence that thickening and calcification in aortic valve disease is a complex inflammatory process and not simply age-related degeneration. Both aortic sclerosis and stenosis represent phenotypic expressions of one disease continuum. Patients with symptomatic severe aortic stenosis benefit from aortic valve replacement. However, management in the absence of symptoms remains challenging. While a delay of aortic valve replacement due to lack of symptom recognition may result in a dismal outcome, unselected premature aortic valve replacement may be associated with unbalanced risks of cardiac surgery. Echocardiography is the standard for evaluating the severity of aortic stenosis; however, most of the current echocardiographic parameters have limitations in predicting the onset of symptoms. This review summarizes the current guidelines and the emerging application of echocardiographic techniques in the management of asymptomatic severe aortic stenosis.     

Forest Structure and Community Composition of Cochin Mangroves,South-West Coast of India

This study presents the structural characteristics of Cochin mangroves in Kerala for proposing suitable management and rejuvenation measures of degrading mangrove habitats. The floristic diversity of mangroves revealed 14 species of true mangroves belonging to six families. Multivariate analysis of true mangroves belonging to selected mangrove forests of the study area based on density could be classified into four floristic groups, a water front or low–tide zonation, mid-tide preferring species, high tide and landward zonation. Shannon Weiner index of the three stations revealed that Site I was having higher value (H′ = 2.66) followed by Site II (H′ = 2.01) and Site III (H′ = 1.595). The density of the mangroves varied significantly with sites and species (Global R = 0.537, P < 0.001). The diameter at breast height (DBH) in the study area revealed that most of the species came under 1–10 cm DBH class. The overall structural data (including Importance Value Index, DBH and basal area) showed that Site III, the Mangalavanam forest was having more structural development and could be considered as matured forest whereas, Site I, Aroor is a maturing forest and Site II, Malippuram is the least matured forest from the study. The Importance Value Index and basal area of each species could be used for analysing the maturity of the forest and habitat preferences for restoration programmes of the degraded ecosystems.     

Left ventricular isovolumic flow sequence during sinus and paced rhythms: new insights from use of high-resolution Doppler and ultrasonic digital particle imaging velocimetry.

OBJECTIVES: We sought to clarify the role of isovolumic intervals during a cardiac cycle by in vivo visualization of left ventricular (LV) intracavitary flow dynamics. BACKGROUND: Asynchronous LV deformation during isovolumic contraction (IVC) and isovolumic relaxation (IVR) might represent a transient feature of myocardial wall mechanics that reverses the direction of blood flow. METHODS: In 10 beating porcine hearts, the changes in LV intracavitary flow were recorded at baseline and after LV epicardial and right atrial pacing with high-resolution Doppler and contrast echocardiography. Two-dimensional vector flow fields were generated offline from B-mode contrast images with particle imaging velocimetry. RESULTS: During IVC, flow from the LV apex accelerated toward the base, whereas blood from the base was redirected toward the outflow through formation of an anterior vortex. Conversely, during IVR, flow was initially directed toward the apex and then briefly reversed toward the base. Epicardial pacing from the LV base altered the stages of flow redirection during the pre-ejection period and delayed mitral valve closure (28 +/- 14 ms vs. 61 +/- 13 ms, p < 0.001) and aortic valve opening (77 +/- 18 ms vs. 111 +/- 18 ms, p = 0.004). CONCLUSIONS: Isovolumic intervals are not periods of hemodynamic stasis but, rather, phases with dynamic changes in intracavitary flow. Experimentally induced aberrant epicardial electrical activation alters stages of flow redirection and prolongs the pre-ejection period. Normal electromechanical activation through the His-Purkinje system in mammalian hearts maintains an inherent synchrony with the sequence of intracavitary flow redirection.     

Patent foramen ovale in cryptogenic stroke: current understanding and management options

There is increasing interest in the association between patent foramen ovale (PFO) and documented stroke of unknown cause, commonly referred to as cryptogenic stroke. We reviewed the literature and, on the basis of the available data, designed a diagnostic and treatment algorithm for patients with PFO and cryptogenic stroke. Patent foramen ovale is relatively common in the general population, but its prevalence is higher in patients with cryptogenic stroke. Importantly, paradoxical embolism through a PFO should be strongly considered in young patients with cryptogenic stroke. There is no consensus on the optimal management strategy, but treatment options include antiplatelet agents, warfarin sodium, percutaneous device closure, and surgical closure. High-risk features in the patient's history (ie, temporal association between Valsalva-inducing maneuvers and stroke, coexisting hypercoagulable state, recurrent strokes, and PFO with large opening, large right-to-left shunt, or right-to-left shunting at rest, and a coexisting atrial septal aneurysm) should prompt PFO closure.