Steven J. Lester

A simple method for noninvasive estimation of pulmonary vascular resistance

OBJECTIVES We sought to test whether the ratio of peak tricuspid regurgitant velocity (TRV, ms) to the right ventricular outflow tract time-velocity integral (TVI(RVOT), cm) obtained by Doppler echocardiography (TRV/TVI(RVOT)) provides a clinically reliable method to determine pulmonary vascular resistance (PVR). BACKGROUND Pulmonary vascular resistance is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. Right-heart catheterization, with its associated disadvantages, is required to determine PVR. However, a reliable noninvasive method is unavailable. METHODS Simultaneous Doppler echocardiographic examination and right-heart catheterization were performed in 44 patients. The ratio of TRV/TVI(RVOT) was then correlated with invasive PVR measurements using regression analysis. An equation was modeled to calculate PVR in Wood units (WU) using echocardiography, and the results were compared with invasive PVR measurements using the Bland-Altman analysis. Using receiver-operating characteristics curve analysis, a cutoff value for the Doppler equation was generated to determine PVR >2WU. RESULTS As calculated by Doppler echocardiography, TRV/TVI(RVOT) correlated well (r = 0.929, 95% confidence interval 0.87 to 0.96) with invasive PVR measurements. The Bland-Altman analysis between PVR obtained invasively and that by echocardiography, using the equation: PVR = TRV/TVI(RVOT) x 10 + 0.16, showed satisfactory limits of agreement (mean 0 +/- 0.41). A TRV/TVI(RVOT) cutoff value of 0.175 had a sensitivity of 77% and a specificity of 81% to determine PVR >2WU. CONCLUSIONS Doppler echocardiography may provide a reliable, noninvasive method to determine PVR.

Carotid Intima-Media Thickness and Coronary Artery Calcium Score as Indications of Subclinical Atherosclerosis

OBJECTIVE To determine the ability of carotid intima-media thickness (CIMT) and coronary artery calcium score (CACS) to detect subclinical atherosclerosis in a young to middle-aged, low-risk, primary-prevention population. PATIENTS AND METHODS Patients aged 36 to 59 years who underwent determination of CIMT and CACS at our institution between May 1, 2004, and April 1, 2008, were included in the study. Those with diabetes mellitus or a history of coronary, peripheral, or cerebral vascular disease were excluded. Other information, such as Framingham risk score (FRS), was obtained by a review of clinical and laboratory data. RESULTS Of 118 patients, 89 (75%) had a CACS of zero and 94 (80%) were men; mean ± SD age was 48.9±5.7 years. The mean FRS of this group was 4.0; 86 patients (97%) were considered at low risk ( CONCLUSION Subclinical vascular disease can be detected by CIMT evaluation in young to middle-aged patients with a low FRS and a CACS of zero. These findings have important implications for vascular disease screening and the implementation of primary-prevention strategies.

Epicardial Fat: An Additional Measurement for Subclinical Atherosclerosis and Cardiovascular Risk Stratification?

BACKGROUND The value of epicardial adipose tissue (EAT) thickness as determined by echocardiography in cardiovascular risk assessment is not well understood. The aim of this study was to determine the associations between EAT thickness and Framingham risk score, carotid intima media thickness, carotid artery plaque, and computed tomographic coronary calcium score in a primary prevention population. METHODS Patients presenting for cardiovascular preventive care (n = 356) who underwent echocardiography as well as carotid artery ultrasound and/or coronary calcium scoring were included. RESULTS EAT thickness was weakly correlated with Framingham risk score. The prevalence of carotid plaque was significantly greater in those with EAT thickness ≥ 5.0 mm who either had low Framingham risk scores or had body mass indexes ≥ 25 kg/m(2), compared with those with EAT thickness <5.0 mm. No significant association between EAT thickness and carotid intima-media thickness or coronary calcium score existed. CONCLUSION EAT thickness ≥ 5.0 mm may identify an individual with a higher likelihood of having detectable carotid atherosclerosis.

Noninvasive assessment of pulmonary vascular resistance by Doppler echocardiography.

BACKGROUND The ratio of tricuspid regurgitation velocity (TRV) to the time-velocity integral of the right ventricular outflow tract (TVIRVOT) has been studied as a reliable measure to distinguish elevated from normal pulmonary vascular resistance (PVR). The equation TRV/TVIRVOT × 10 + 0.16 (PVRecho) has been shown to provide a good noninvasive estimate of PVR. However, its role in patients with significantly elevated PVR (> 6 Wood units [WU]) has not been conclusively evaluated. The aim of this study was to establish the validity of the TRV/TVIRVOT ratio as a correlate of PVR. The role of TRV/TVIRVOT was also compared with that of a new ratio, TRV(2)/TVIRVOT, in patients with markedly elevated PVR (>6 WU). METHODS Data from five validation studies using TRV/TVIRVOT as an estimate of PVR were compared with invasive PVR measurements (PVRcath). Multiple linear regression analyses were generated between PVRcath and both TRV/TVIRVOT and TRV(2)/TVIRVOT. Both PVRecho and a new derived regression equation based on TRV(2)/TVIRVOT: 5.19 × TRV(2)/TVIRVOT - 0.4 (PVRecho2) were compared with PVRcath using Bland-Altman analysis. Logistic models were generated, and cutoff values for both TRV/TVIRVOT and TRV(2)/TVIRVOT were obtained to predict PVR > 6 WU. RESULTS One hundred fifty patients remained in the final analysis. Linear regression analysis between PVRcath and TRV/TVIRVOT revealed a good correlation (r = 0.76, P < .0001, Z = 0.92). There was a better correlation between PVRcath and TRV(2)/TVIRVOT (r = 0.79, P < .0001, Z = -0.01) in the entire cohort as well as in patients with PVR > 6 WU. Moreover, PVRecho2 compared better with PVRcath than PVRecho using Bland-Altman analysis in the entire cohort and in patients with PVR > 6 WU. TRV(2)/TVIRVOT and TRV/TVIRVOT both predicted PVR > 6 WU with good sensitivity and specificity. CONCLUSIONS TRV/TVIRVOT is a reliable method to identify patients with elevated PVR. In patients with TRV/TVIRVOT > 0.275, PVR is likely > 6 WU, and PVRecho2 derived from TRV(2)/TVIRVOT provides an improved noninvasive estimate of PVR compared with PVRecho.

Carotid ultrasound identifies high risk subclinical atherosclerosis in adults with low Framingham risk scores

BACKGROUND Worldwide, cardiovascular (CV) disease remains the most common cause of morbidity and mortality. Although effective in predicting CV risk in select populations, the Framingham risk score (FRS) fails to identify many young individuals who experience premature CV events. Accordingly, the aim of this study was to determine the prevalence of high-risk carotid intima-media thickness (CIMT) or plaque, a marker of atherosclerosis and predictor of CV events, in young asymptomatic individuals with low and intermediate FRS (<2% annualized event rate) using the carotid ultrasound protocol recommended by the American Society of Echocardiography and the Society of Vascular Medicine. METHODS Individuals aged < or = 65 years not taking statins and without diabetes mellitus or histories of coronary artery disease underwent CIMT and plaque examination for primary prevention. Clinical variables including lipid values, family history of premature coronary artery disease, and FRS and subsequent pharmacotherapy recommendations were retrospectively collected for statistical analysis. RESULTS Of 441 subjects (mean age, 49.7 + or - 7.9 years), 184 (42%; 95% confidence interval, 37.3%-46.5%) had high-risk carotid ultrasound findings (CIMT > or = 75th percentile adjusted for age, gender, and race or presence of plaque). Of those with the lowest FRS of < or =5% (n = 336) (mean age, 48.0 + or - 7.6 years; mean FRS, 2.5 + or - 1.5%), 127 (38%; 95% confidence interval, 32.6%-43.0%) had high-risk carotid ultrasound findings. For individuals with FRS < or = 5% and high-risk carotid ultrasound findings (n = 127; mean age, 47.3 + or - 8.1 years; mean FRS, 2.5 + or - 1.5%), lipid-lowering therapy was recommended by their treating physicians in 77 (61%). CONCLUSIONS Thirty-eight percent of asymptomatic young to middle-aged individuals with FRS < or = 5% have abnormal carotid ultrasound findings associated with increased risk for CV events. Pharmacologic therapy for CV prevention was recommended in the majority of these individuals. The lack of radiation exposure, relatively low cost, and ability to detect early-stage atherosclerosis suggest that carotid ultrasound for CIMT and plaque detection should continue to be explored as a primary tool for CV risk stratification in young to middle-aged adults with low FRS.

Subclinical Atherosclerosis: Evolving Role of Carotid Intima‐Media Thickness

Cardiovascular risk factors have utility in risk prediction but have limitations in predicting individual risk. Identifying an individuals risk remains a challenge. Emerging technologies such as carotid artery ultrasonography and measures of carotid intima-media thickness (CIMT) may be useful in identifying the susceptible patient who may benefit from more aggressive preventive therapy. This screening test is noninvasive, reproducible, inexpensive, and radiation-free. Recent data have improved our understanding of the application of CIMT as a screening tool for cardiovascular disease. CIMT measurement may place an individual into a higher- or lower-risk category, allowing for appropriate institution of preventive strategies.

Incidence of subclinical atherosclerosis as a marker of cardiovascular risk in retired professional football players.

The purpose of this study was to evaluate subclinical atherosclerosis in retired professional football players. Two hundred one healthy former professional football players (mean age 50.8 years; mean body mass index 31.5 kg/m(2)) were screened for the prevalence of cardiovascular risk factors, metabolic syndrome, and subclinical atherosclerosis by carotid artery ultrasound and compared with a cohort of men of similar body mass index referred for the assessment of subclinical atherosclerosis by carotid ultrasound. The prevalence of carotid artery plaque in the players was not significantly different from that of the body mass index-matched patients (33.3% vs 29.3%, p = 0.45). For the 2 groups, the prevalence of carotid artery plaque was >3 times higher than that reported in general population studies of patients with the same age range, gender, and exclusions. Metabolic syndrome prevalence was higher in linemen than in nonlinemen (45.8% vs 22.5%, p = 0.001), but there was no statistical difference in plaque presence between linemen and nonlinemen (27.1% vs 35.9%, p = 0.23). In conclusion, despite their elite athletic histories, former professional football players have a similar prevalence of advanced subclinical atherosclerosis as a clinically referred population of overweight and obese men.

Contrast Echocardiography: Beyond a Black Box Warning?

With respect to echocardiographic procedures, time and cost efficiency should be viewed in terms of the time and cost required to address the clinical reason justifying the examination. From this perspective, excellence in echocardiography may be viewed as correctly answering the clinical question, based on unequivocal diagnostic information, and doing so efficiently. In general, this can be achieved only if all tools available to maximize image quality are used appropriately. The article by Drs Bhatia and Senior, “Contrast Echocardiography: Evidence for Clinical Use,” in this issue of the Journal nicely outlines the published scientific evidence that the judicious use of microbubble contrast agents to support an echocardiographic evaluation is an important part of the quest for excellence. Reluctance to use contrast agents has, by and large, been attributed to the misconception that there are adverse consequences on provider time and reimbursement. The United States Food and Drug Administration (FDA) recently issued a warning to health care professionals regarding the use of ultrasound microbubble contrast agents in echocardiography, namely, perflutren lipid microspheres (Definity, Bristol-Myers Squibb, New York, NY) and perflutren protein-type A microspheres for injection (Optison, General Electric, Fairfield, CT). As a result, the manufacturers of these agents have agreed to revise the labeling for these products to optimize their safe use. This warning may result in further reluctance to include contrast echocardiography in the diagnostic armamentarium of cardiac ultrasound. Imagers ensure that the best interest of the patient is met only when the images obtained can best answer the clinical question posed. Echocardiography has unparalleled temporal resolution, a harmless energy source, and a configurability that makes it the most versatile and useful tool in the noninvasive evaluation of patients with cardiovascular disease. Drs Bhatia and Senior outline the evidence that contrast enhancement may salvage an otherwise “nondiagnostic” examination and improve the accuracy and reproducibility of measures of ventricular function. When to contrast enhance an image is generally not based on a suspected diagnosis or patient body habitus, but rather on image quality, and in the absence of a contraindication is strongly encouraged when left ventricular endocardial border delineation is suboptimal ( 2 endocardial segments poorly visualized). Novel to surface echocardiography, since the advent of contrast for endocardial border definition, is the reality that achieving excel-

Aortic Valve Stenosis: To the Gradient and Beyond—The Mismatch Between Area and Gradient Severity

The clinical severity of aortic stenosis (AS) is based largely on symptoms. However, AS severity is primarily determined by estimating the aortic valve area (AVA) and pressure gradients (ΔP). Conditions may arise in which there is a mismatch in severity between AVA and ΔP determinations secondary to errors in measurement and/or assumption, alterations of flow, or variations in the magnitude of pressure recovery. The cause of discrepancy between area and gradient determinations must be deciphered so as to best counsel patients on the most ideal treatment strategy.

Effect of Echocardiographic Contrast on Velocity Vector Imaging Myocardial Tracking

BACKGROUND Two-dimensional speckle tracking is an evolving ultrasound technology that allows objective evaluation of left ventricular function. The effect of echocardiographic contrast with 2-dimensional speckle tracking image processing is poorly defined. METHODS A total of 11 patients undergoing clinically indicated transthoracic echocardiography who also required echocardiographic contrast for left ventricular endocardial border enhancement were prospectively studied. Offline velocity vector imaging analysis was performed to calculate global and regional longitudinal strain from the apical 4-chamber view while corresponding circumferential strain was obtained from the parasternal short-axis view at the papillary muscle level. Images were isochronally normalized and the systolic phase was studied precontrast and postcontrast opacification. RESULTS Intraclass correlation coefficients were high for global circumferential strain in the short-axis view (0.77) and global longitudinal strain in the apical 4-chamber view (0.87) precontrast and postcontrast. Significant regional variability was present, more pronounced in the apical 4-chamber view (intraclass correlation coefficient 0.24-0.64) versus short-axis view (intraclass correlation coefficient 0.64-0.68). CONCLUSIONS Velocity vector imaging is able to quantify global and regional strain with and without contrast. There is, however, wide interindividual variability in regional strain quantification with and without contrast, potentially limiting the clinical applicability.