Subodh B. Joshi

Ultra-low-dose intra-arterial contrast injection for iliofemoral computed tomographic angiography.

OBJECTIVES This study sought to evaluate the feasibility of using ultra-low-dose intra-arterial contrast injection for iliofemoral computed tomographic (CT) angiography to follow diagnostic cardiac catheterization. BACKGROUND Cardiovascular interventions such as percutaneous aortic valve replacement require transfemoral delivery of large-bore intra-arterial catheters; therefore, pre-procedural assessment of aortoiliofemoral anatomy is important. CT angiography is ideal for this purpose but requires a large volume of intravenous contrast. METHODS Consecutive patients requiring evaluation of aortoiliofemoral anatomy underwent conventional anteroposterior projection iliac angiography during cardiac catheterization. A pigtail catheter was left in situ in the infrarenal abdominal aorta, and patients were transferred to the CT suite. Subsequently, 10 to 15 ml of contrast diluted with normal saline was injected intra-arterially via the pigtail catheter while a spiral CT of the abdomen and pelvis was acquired. Conventional angiographic and CT images were analyzed independently to assess suitability for large-bore (7-mm-diameter)intra-arterial catheter access. RESULTS Excellent CT image quality was achieved in 34 of 37 patients (92%). The mean contrast dose for CT was 12 +/- 2 ml. In 9 patients (24%), CT changed the assessment of femoral access feasibility. Furthermore, in another 7 patients (19%), unfavorable anatomy as shown by CT directed the avoidance of a particular side. Overall, CT findings altered the interventional approach in 16 patients (43%). There was no significant deterioration detected in renal function after coronary and CT angiography (estimated glomerular filtration rate 54.8 +/- 3.8 ml/min before 53.3 +/- 3.9 ml/min after, p = 0.55). CONCLUSIONS High-quality aortoiliofemoral CT angiography can be obtained with a technical success rate of >90% using 10 to 15 ml of contrast injected via a catheter in the abdominal aorta, and offers an alternative to conventional X-ray or CT angiography with high-volume intravenous contrast injection.

Association of pericardial fat and coronary high-risk lesions as determined by cardiac CT.

OBJECTIVE Pericardial adipose tissue (PAT) is a pathogenic fat depot associated with coronary atherosclerosis and cardiovascular events. We hypothesized that higher PAT is associated with coronary high-risk lesions as determined by cardiac CT. METHODS We included 358 patients (38% female; median age 51 years) who were admitted to the ED with acute chest pain and underwent 64-slice CT angiography. The cardiac CT data sets were assessed for presence and morphology of CAD and PAT. Coronary high-risk lesions were defined as >50% luminal narrowing and at least two of the following characteristics: positive remodeling, low-density plaque, and spotty calcification. PAT was defined as any pixel with CT attenuation of -190 to -30 HU within the pericardial sac. RESULTS Based on cardiac CT, 50% of the patients (n=180) had no CAD, 46% (n=165) had CAD without high-risk lesions, and 13 patients had CAD with high-risk lesions. The median PAT in patients with high-risk lesions was significantly higher compared to patients without high-risk lesions and without any CAD (151.9 [109.0-179.4]cm(3) vs. 110.0 [81.5-137.4]cm(3), vs. 74.8 [58.2-111.7]cm(3), respectively p=0.04 and p<0.0001). These differences remained significant after adjusting for traditional risk factors including BMI (all p<0.05). The area under the ROC curve for the identification of high-risk lesions was 0.756 in a logistic regression model with PAT as a continuous predictor. CONCLUSION PAT volume is nearly twice as high in patients with high-risk coronary lesions as compared to those without CAD. PAT volume is significantly associated with high risk coronary lesion morphology independent of clinical characteristics and general obesity.

A Computed Tomography-Based Coronary Lesion Score to Predict Acute Coronary Syndrome Among Patients With Acute Chest Pain and Significant Coronary Stenosis on Coronary Computed Tomographic Angiogram

We tested the hypothesis that morphologic lesion assessment helps detect acute coronary syndrome (ACS) during index hospitalization in patients with acute chest pain and significant stenosis on coronary computed tomographic angiogram (CTA). Patients who presented to an emergency department with chest pain but no objective signs of myocardial ischemia (nondiagnostic electrocardiogram and negative initial biomarkers) underwent CT angiography. CTA was analyzed for degree and length of stenosis, plaque area and volume, remodeling index, CT attenuation of plaque, and spotty calcium in all patients with significant stenosis (>50% in diameter) on CTA. ACS during index hospitalization was determined by a panel of 2 physicians blinded to results of CT angiography. For lesion characteristics associated with ACS, we determined cutpoints optimized for diagnostic accuracy and created lesion scores. For each score, we determined the odds ratio (OR) and discriminatory capacity for the prediction of ACS. Of the overall population of 368 patients, 34 had significant stenosis and 21 of those had ACS. Scores A (remodeling index plus spotty calcium: OR 3.5, 95% confidence interval [CI] 1.2 to 10.1, area under curve [AUC] 0.734), B (remodeling index plus spotty calcium plus stenosis length: OR 4.6, 95% CI 1.6 to 13.7, AUC 0.824), and C (remodeling index plus spotty calcium plus stenosis length plus plaque volume <90 HU: OR 3.4, 95% CI 1.5 to 7.9, AUC 0.833) were significantly associated with ACS. In conclusion, in patients presenting with acute chest pain and stenosis on coronary CTA, a CT-based score incorporating morphologic characteristics of coronary lesions had a good discriminatory value for detection of ACS during index hospitalization.

Can Acute Occlusion of the Left Anterior Descending Coronary Artery Produce a Typical “Takotsubo” Left Ventricular Contraction Pattern?

The takotsubo syndrome (TS) takes its name from a distinctive left ventricular (LV) contraction abnormality. Patients with this disorder present with clinical findings of an acute ischemic event. Despite the absence of obstructive coronary artery disease, there is a hallmark LV contraction abnormality, namely hypercontractility of the base but akinesia or dyskinesis of the apex. Many discount a role for the epicardial coronary arteries in this disorder because the LV contraction abnormality appears to overlap >1 vascular territory. To test this assumption we analyzed the contraction pattern associated with left anterior descending coronary artery (LAD) occlusion. From May to September 2006, 43 patients underwent primary percutaneous coronary intervention for acute ST-elevation myocardial infarction due to LAD occlusion. Their left ventriculograms were randomly mixed with those of 47 patients clinically labeled as TS. Two reviewers unaware of the clinical diagnosis characterized the LV contraction pattern of all 90 as typical of TS or not. In 6 of the 43 patients (14%) with primary PCI the 2 reviewers considered the pattern to be typical, and in 5 (12%), 1 of 2 reviewers did. Thus, in 26% >/=1 reviewer believed that the pattern associated with LAD occlusion was typical of TS. In conclusion, the characteristic TS contraction pattern may be seen in some patients with acute occlusion of the LAD. It would be premature to dismiss the possibility of transient LAD occlusion as part of the pathogenesis of that disorder.

Accuracy of Computed Tomographic Angiography for Stenosis Quantification Using Quantitative Coronary Angiography or Intravascular Ultrasound as the Gold Standard

Computed tomographic angiography (CTA) is considered to have limited accuracy for quantifying exact percent diameter stenosis in coronary arteries. However, most studies evaluating CTA use quantitative coronary angiography (QCA) as the gold standard, a technique with its own limitations. We sought to determine whether CTA measurements of stenosis severity correlate better with intravascular ultrasound (IVUS) than with QCA. Luminal dimensions of 67 de novo coronary lesions were measured by CTA, IVUS, and QCA. IVUS was performed when lesion severity by angiography was equivocal. Mean percent diameter stenosis by QCA was 51 +/- 9.8% and mean IVUS minimal luminal area was 3.8 +/- 1.8 mm(2). There was a moderate correlation between CTA minimal luminal area and IVUS minimal luminal area (r(2) = 0.41, p <0.001), but no relation between CTA and QCA measurements of minimal luminal diameter (r(2) = 0.01, p = 0.57) or diameter stenosis (r(2) = 0.02, p = 0.31). There was also no relation between IVUS minimal luminal area and QCA diameter stenosis (r(2) = 0.01, p = 0.50). When lesions with moderate or severe calcification were excluded, the correlation between CTA minimal luminal area and IVUS minimal luminal area was good (r(2) = 0.68, p <0.001). In conclusion, in this cohort of patients with intermediate-grade lesions on cardiac catheterization, absolute measurements of stenosis severity on CTA correlated with IVUS but not with QCA. Our findings suggest that limitations of quantitative coronary angiography as a gold standard need to be considered in studies evaluating the accuracy of coronary CTA.

Mechanism of Paradoxical Ventricular Septal Motion After Coronary Artery Bypass Grafting

Paradoxical septal motion is commonly noted on echocardiography after coronary artery bypass grafting (CABG), but its mechanism is unclear. Cardiac magnetic resonance imaging was performed before and 3 months after CABG in 23 patients. On a mid-left ventricular short-axis cine image, the motion of myocardial landmarks during the cardiac cycle was ascertained relative to a stationary anterior reference point. Before CABG, the movement of the ventricular septum in systole was either posterior or neutral (median -2 mm) in 19 patients, whereas after CABG, the septum moved anteriorly in all 23 patients (+4 mm; p<0.001). (A positive sign indicates anterior motion in ventricular systole, and a negative sign denotes posterior motion.) The motion of the right ventricular free wall was reduced after CABG (-5 vs -3 mm; p=0.002), whereas anterior movement of the lateral left ventricular wall in systole increased (+4 vs +9 mm; p<0.001). There was a positive correlation between degree of anterior movement of the ventricular septum and right ventricular ejection fraction (r=0.47, p=0.023). In conclusion, after CABG, the entire left ventricle translocated anteriorly in systole. Despite preserved right ventricular function, there was restricted motion of the right ventricular free wall suggestive of postoperative adhesions. The pattern of movement observed offers a sound explanation for postoperative paradoxical septal motion.

Viability imaging by cardiac computed tomography

First-pass perfusion and delayed enhancement cardiac imaging have been shown to be feasible by cardiac CT. However, questions remain about its reliability, and ideal scanning parameters have yet to be fully established. In general, scar imaging with cardiac CT typically requires 2 scans, with first-pass perfusion information derived from the same data set used to visualize the coronary arteries. Reduced contrast enhancement on first-pass cardiac CT images represents reduced perfusion. Higher doses of contrast are required to perform viability imaging by cardiac CT. Approximately 10 minutes after contrast administration, viability information is obtained by performing a second (noncontrast) scan. In addition to the concepts of perfusion and viability imaging by cardiac CT, we review parameters such as scan timing, tube settings, contrast delivery, reconstruction, and postprocessing techniques, as well as the associated pitfalls and technical limitations in perfusion and viability imaging by cardiac CT.

Comparison of Intravascular Ultrasound to Contrast-Enhanced 64-Slice Computed Tomography to Assess the Significance of Angiographically Ambiguous Coronary Narrowings

The efficacy of contrast-enhanced multislice computed tomography (MSCT) for assessment of ambiguous lesions is unknown. We compared both quantitative coronary angiography (QCA) and MSCT to the gold standard for a significant stenosis-minimum luminal area (MLA) by intravascular ultrasound (IVUS)-in 51 patients (64 +/- 10 years old, 19 men) with 69 angiographically ambiguous, nonleft main lesions. The MSCT was performed 17 +/- 18 days before IVUS analysis. Overall diameter stenosis by QCAwas 51.0 +/- 9.8%; 39 of 51 patients (76%) eventually underwent revascularization (38 by percutaneous coronary intervention and 1 by coronary artery bypass graft). By univariate analysis, minimum luminal diameter, MLA, lumen visibility by MSCT, and minimum luminal diameter by QCA were significant predictors of MLA by IVUS <or=4.0 mm(2). In mildly calcified lesions (calcium burden by MSCT <or=1), MLA by MSCT was a much better predictor than in more calcified lesions. By multivariate logistic regression analysis, only MLA by MSCT (odds ratio 0.754, 95% confidence interval 0.571 to 0.995, p = 0.0458) was predictive of MLA by IVUS <or=4.0 mm(2). In conclusion, in angiographically ambiguous lesions in which QCA does not distinguish significantly from nonsignificant stenosis, MSCT-measured MLA can predict significant stenosis with MLA <or=4.0 mm(2) measured by IVUS.

Right ventricular function after coronary artery bypass graft surgery—a magnetic resonance imaging study

BACKGROUND A reduction in right ventricular function commonly occurs in the early postoperative period after coronary artery bypass graft surgery (CABG). We sought to determine the longer-term effect of CABG on right ventricular function. METHODS Cardiac magnetic resonance imaging was performed before and approximately 3 months after surgery in 28 patients undergoing elective CABG. Right ventricular (RV) ejection fraction was assessed by planimetry of electrocardiographically gated cine images. RESULTS There was a statistically significant increase in left ventricular ejection fraction from 50% to 58% (P=.003) after CABG. RV ejection fraction also increased from 54% to 60% (P=.002). In patients with lower baseline RV ejection fraction (below the median, < 53%), this parameter improved from 47% to 57% (P<.001). Both on-pump (47% vs. 62%, P=.003) as well as off-pump CABG (47% vs. 55%, P=.009) lead to an improvement in RV function in patients in the initial low RV ejection fraction group. CONCLUSION Long-term right ventricular function was not adversely affected by CABG. An improvement in RV function occurred after surgery in patients with low baseline RV ejection fraction and was similar in patients who underwent surgery with or without cardiopulmonary bypass.

The predictive value of computed tomography calcium scores: a comparison with quantitative volumetric intravascular ultrasound

OBJECTIVE To evaluate the relationship between coronary artery calcium scoring (CACS) and intravascular ultrasound (IVUS) calcification and disease severity. METHODS Forty-five angina patients who underwent CACS 18+/-23 days before IVUS were studied. The CACS was recorded for each lesion matched to a specific IVUS lesion. Cross-sectional area measurements of the external elastic membrane, lumen area, plaque and media, and plaque burden were performed. The arc and length of calcification were measured. RESULTS There were 106 calcified lesions detected by IVUS. Eighty-five of those lesions (80%) were detected by CACS, but 21 calcified lesions (20%) were missed. Fourteen (50%) out of 28 of the lesions with an IVUS-calcium arc below the 25th percentile (51.4 degrees ) were detected by CACS vs. 91% of lesions with an IVUS-calcium arc >51.4 degrees (P<.05). Similarly, 21 (58%) of 36 lesions <or=3 mm in length were detected vs. 91% of lesions >3 mm (P<.05). We divided IVUS-calcified lesions into CACS <or=10 and >10. Mean plaque burden, calcified length, and arc of calcium increased significantly, while minimum lumen area decreased with increasing CACS. There was the same tendency in culprit and nonculprit calcified lesions, respectively. Multivariate analysis showed a calcified length (regression coefficient=8.718, 95% CI 4.668-12.77, P<.001) and an arc of calcium (regression coefficient=2.789, 95% CI 1.419-4.119, P<.001) were significant predictors for CACS. CONCLUSIONS This study suggests that a CACS could evaluate coronary calcium burden noninvasively through the accurate estimation of calcium-arc and length.