Determination of left ventricular mass on cardiac computed tomographic angiography.

RATIONALE AND OBJECTIVES: Left ventricular hypertrophy (LVH) is associated with an increased risk of cardiac death. The present study evaluates whether using computed tomographic (CT)-derived criteria for normal myocardial mass can improve detection of LVH on CT angiography (CTA). MATERIALS AND METHODS: A total of 2238 subjects (63 +/- 9 years, 27% female) who underwent CTA were studied. To identify normal limits for CT-derived myocardial mass, we studied normal subjects (those without diabetes, hypertension, congestive heart failure, or coronary artery disease). Left ventricular mass (LVM) was measured manually using two different workstations. The CT criteria of LVH was defined as LVM above the 97th percentile per gender and compared to echocardiographic criteria (110 g/m(2) in women; 124 g/m(2) in men), and specificity and sensitivity of both models to detect LVH were calculated. RESULTS: The LVM was higher in men than women in normal cohorts (75.5 +/- 14.0 vs. 63.1 +/- 12.8 g/m(2), P = .001 with electron beam CTA and 78.5 +/- 11.9 vs. 65.0 +/- 9.2 g/m(2), P = .001 with 64 multidetector [MD] CT, respectively). The coefficient of variation between electron beam CTA and 64 MDCT for measuring LVM was 3.1%. Comparing the new CTA/64 MDCT criteria of LVH (103.0 g/m(2) in men; 89.0 g/m(2) in women) to the previous echocardiographic criteria of LVH, the specificity in women and men decreased from 100% in both genders by echocardiography to 91.8% and 92.6%, respectively, but the sensitivity increased from 42.0% to 100% and from 41.1% to 100%. CONCLUSION: This study suggests that CT-measured LVM has low variability and normal values based on CT criteria will potentially increase the early detection of LVH.

Accurate measurement of mitral annular dimensions by echocardiography: importance of correctly aligned imaging planes and anatomic landmarks.

BACKGROUND: Mitral annular (MA) dimensions obtained by traditional two-dimensional echocardiography are poorly standardized and do not adhere to anatomic principles. Correct anatomic imaging planes of the anterior-posterior (AP) and commissure-commissure (CC) axes of the mitral annulus were compared with the traditional method and correlated with cardiac computed tomography (CT). METHODS: Seventeen subjects underwent traditional and correct anatomic imaging planes echocardiography and cardiac CT. The traditional method was obtained in the parasternal long-axis and apical 4-chamber views. Correct anatomic imaging planes were obtained in the apical long-axis view. The traditional and correct anatomic images planes methods were correlated with cardiac CT. RESULTS: The traditional method of MA measurement correlated poorly with cardiac CT (AP axis: r = 0.13; CC axis: r = 0.02). The correct anatomic imaging planes method of MA measurement correlated very well with cardiac CT (AP axis: r = 0.96; CC axis: r = 0.91) (P < .05). CONCLUSIONS: The correct anatomic imaging planes method provides accurate measurement of the AP and CC axes of the mitral annulus by adhering to geometric and anatomic principles.

Detection of noncalcified and mixed plaque by multirow detector computed tomography.

New tomographic cardiovascular imaging tests, such as intravascular ultrasonography and coronary computed tomography angiography, can be used to assess atherosclerotic plaques for the characterization and early staging of coronary artery disease (CAD). Although intravascular ultrasonography provides high-resolution images that are capable of revealing early preclinical CAD, it is a highly invasive technique used clinically only in conjunction with coronary interventions. Multidetector computed tomography angiography, which is noninvasive and corresponds well with plaque histology, shows promise as a diagnostic method for CAD and can provide general evaluation of noncalcified and mixed plaque composition. The current generation of 64-slice computed tomography scanners have high accuracy for detection of lesions obstructing more than 50% of the lumen, with sensitivity, specificity, and positive and negative predictive values all over 90% in patients without known CAD. They may have an important role in characterizing high-risk noncalcified and mixed plaques. Review of the currently available literature suggests that tissue density measured by multidetector computed tomography can be used to accurately characterize coronary atherosclerotic plaque composition. With further advances in tomographic angiography, the goal will be to detect plaques earlier in the development of CAD and to characterize the plaques most likely to generate a clinical event.

Tedisamil and lidocaine enhance each other's antiarrhythmic activity against ischaemia-induced arrhythmias in rats.

1. Combinations of the action potential-widening drug tedisamil (Class III antiarrhythmic activity), and the inactivated state sodium channel blocker lidocaine (Class Ib antiarrhythmic activity) were assessed for antiarrhythmic actions in a rat model of ischaemia-induced arrhythmias and for electrophysiological actions in normal rat myocardial tissue. 2. Both tedisamil and lidocaine dose-dependently suppressed ischaemia-induced arrhythmias. The ED(50) values were 3.0+/-1.3 and 4.9+/-0.6 micro mol kg(-1) min(-1), respectively. 3. Combinations of the two drugs acted synergistically such that the ED(50) for tedisamil was reduced to 0.8+/-0.2 micro mol kg(-1) min(-1) in the presence of 2 micro mol kg(-1) min(-1) lidocaine. Similarly, the ED(50) for lidocaine was reduced to 0.7+/-0.2 micro mol kg(-1) min(-1) in the presence of 2 micro mol kg(-1) min(-1) tedisamil (both P<0.05). 4. In a separate series of experiments in which normal ventricular tissue was electrically stimulated, 2 micro mol kg(-1) min(-1) lidocaine produced a leftward shift in the dose-response curve for tedisamil's effect on effective refractory period (P<0.05). This dose of lidocaine had no effect on its own. These data indicate that the synergistic actions of combinations of tedisamil and lidocaine were mediated, at least in part, by extension of effective refractory period in normal myocardial tissue. 5. In contrast to the strategy of developing drugs that are selective for a single electrophysiological mechanism, the results of the present study suggest that effective antiarrhythmic drugs might be developed by optimising the combination of two complimentary electrophysiological mechanisms (i.e., action potential-prolonging activity and inactivated state sodium channel blockade).