Saurabh S. Dhawan

Coronary Artery Wall Shear Stress Is Associated With Progression and Transformation of Atherosclerotic Plaque and Arterial Remodeling in Patients With Coronary Artery Disease

Background Experimental studies suggest that low wall shear stress (WSS) promotes plaque development and high WSS is associated with plaque destabilization. We hypothesized that low-WSS segments in patients with coronary artery disease develop plaque progression and high-WSS segments develop necrotic core progression with fibrous tissue regression. Methods and Results Twenty patients with coronary artery disease underwent baseline and 6-month radiofrequency intravascular ultrasound (virtual histology intravascular ultrasound) and computational fluid dynamics modeling for WSS calculation. For each virtual histology intravascular ultrasound segment (n=2249), changes in plaque area, virtual histology intravascular ultrasound–derived plaque composition, and remodeling were compared in low-, intermediate-, and high-WSS categories. Compared with intermediate-WSS segments, low-WSS segments developed progression of plaque area (P=0.027) and necrotic core (P<0.001), whereas high-WSS segments had progression of necrotic core (P<0.001) and dense calcium (P<0.001) and regression of fibrous (P<0.001) and fibrofatty (P<0.001) tissue. Compared with intermediate-WSS segments, low-WSS segments demonstrated greater reduction in vessel (P<0.001) and lumen area (P<0.001), and high-WSS segments demonstrated an increase in vessel (P<0.001) and lumen (P<0.001) area. These changes resulted in a trend toward more constrictive remodeling in low- compared with high-WSS segments (73% versus 30%; P=0.06) and more excessive expansive remodeling in high- compared with low-WSS segments (42% versus 15%; P=0.16). Conclusions Compared with intermediate-WSS coronary segments, low-WSS segments develop greater plaque and necrotic core progression and constrictive remodeling, and high-WSS segments develop greater necrotic core and calcium progression, regression of fibrous and fibrofatty tissue, and excessive expansive remodeling, suggestive of transformation to a more vulnerable phenotype. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT00576576.

Association of coronary wall shear stress with atherosclerotic plaque burden, composition, and distribution in patients with coronary artery disease.

Background Extremes of wall shear stress (WSS) have been associated with plaque progression and transformation, which has raised interest in the clinical assessment of WSS. We hypothesized that calculated coronary WSS is predicted only partially by luminal geometry and that WSS is related to plaque composition. Methods and Results Twenty‐seven patients with coronary artery disease underwent virtual histology intravascular ultrasound and Doppler velocity measurement for computational fluid dynamics modeling for WSS calculation in each virtual histology intravascular ultrasound segment (N=3581 segments). We assessed the association of WSS with plaque burden and distribution and with plaque composition. WSS remained relatively constant across the lower 3 quartiles of plaque burden (P=0.08) but increased in the highest quartile of plaque burden (P<0.001). Segments distal to lesions or within bifurcations were more likely to have low WSS (P<0.001). However, the majority of segments distal to lesions (80%) and within bifurcations (89%) did not exhibit low WSS. After adjustment for plaque burden, there was a negative association between WSS and percent necrotic core and calcium. For every 10 dynes/cm2 increase in WSS, percent necrotic core decreased by 17% (P=0.01), and percent dense calcium decreased by 17% (P<0.001). There was no significant association between WSS and percent of fibrous or fibrofatty plaque components (P=NS). Conclusions In patients with coronary artery disease: (1) Luminal geometry predicts calculated WSS only partially, which suggests that detailed computational techniques must be used to calculate WSS. (2) Low WSS is associated with plaque necrotic core and calcium, independent of plaque burden, which suggests a link between WSS and coronary plaque phenotype. (J Am Heart Assoc. 2012;1:e002543 doi: 10.1161/JAHA.112.002543.)

Coronary angiographic scoring systems: an evaluation of their equivalence and validity.

BACKGROUND Multiple scoring systems have been devised to quantify angiographic coronary artery disease (CAD) burden, but it is unclear how these scores relate to each other and which scores are most accurate. The aim of this study was to compare coronary angiographic scoring systems (1) with each other and (2) with intravascular ultrasound (IVUS)-derived plaque burden in a population undergoing angiographic evaluation for CAD. METHODS Coronary angiographic data from 3600 patients were scored using 10 commonly used angiographic scoring systems and interscore correlations were calculated. In a subset of 50 patients, plaque burden and plaque area in the left anterior descending coronary artery were quantified using IVUS and correlated with angiographic scores. RESULTS All angiographic scores correlated with each other (range for Spearman coefficient [ρ] 0.79-0.98, P < .0001); the 2 most widely used scores, Gensini and CASS-70, had a ρ = 0.90 (P < .0001). All scores correlated significantly with average plaque burden and plaque area by IVUS (range ρ 0.56-0.78, P < .0001 and 0.43-0.62, P < .01, respectively). The CASS-50 score had the strongest correlation (ρ 0.78 and 0.62, P < .0001) and the Duke Jeopardy score the weakest correlation (ρ 0.56 and 0.43, P < .01) with plaque burden and area, respectively. CONCLUSIONS Angiographic scoring systems are strongly correlated with each other and with atherosclerotic plaque burden. Scoring systems therefore appear to be a valid estimate of CAD plaque burden.

Fracture Risk in Men With Congestive Heart Failure: Risk Reduction With Spironolactone

OBJECTIVES The purpose of this study was to determine whether spironolactone use is associated with fractures in men with congestive heart failure (CHF). BACKGROUND In rats with aldosteronism, spironolactone preserves skeletal strength. However, in humans, the relationship of spironolactone to fractures is not known. METHODS The medical records of all male patients with CHF from 1999 to 2005 treated at the Veterans Affairs Medical Center, Memphis, Tennessee, were reviewed (n = 4,735). Odds ratios with 95% confidence intervals of having a fracture associated with spironolactone use were estimated using conditional logistic regression. RESULTS We identified 167 cases with a single-incident fracture and matched these by age and race to 668 control subjects without fractures. After adjustment for covariates, spironolactone use was inversely associated with total fracture (odds ratio: 0.575; 95% confidence interval: 0.346 to 0.955, p = 0.0324). CONCLUSIONS The use of spironolactone is inversely associated with fractures in men with CHF.

Shear stress and plaque development

Although traditional cardiovascular risk factors ‘prime the soil’ for atherogenesis systemically, atherosclerosis primarily occurs in a site-specific manner with a predilection towards the inner wall of curvatures and outer wall of bifurcations with sparing of flow-dividers. Wall shear stress is a frictional force exerted parallel to the vessel wall that leads to alteration of the endothelial phenotype, endothelial cell signaling, gene and protein expression leading to a proinflammatory phenotype, reduced nitric oxide availability and disruption of the extracellular matrix, which in turn leads to plaque development. Clinical and experimental data are emerging that suggest the pathobiology associated with abnormal wall shear stress results in atherosclerotic plaque development and progression.

The role of plasma aminothiols in the prediction of coronary microvascular dysfunction and plaque vulnerability

BACKGROUND Although oxidative stress is considered a key pathogenic step in mediating vascular dysfunction and atherosclerosis development, their association has not been evaluated in human coronary circulation in vivo. Accordingly, we hypothesized that higher oxidative stress would be associated with abnormal coronary epicardial structure and microvascular function. METHODS We measured coronary flow velocity reserve (CFVR) and hyperemic microvascular resistance (HMR) as indices of microvascular function, and epicardial plaque volume and necrotic core using intravascular ultrasound (IVUS) in 47 patients undergoing cardiac catheterization. Plasma glutathione, cystine and their ratio served as measures of oxidative stress while high-sensitivity C-reactive protein (hs-CRP) served as a measure of inflammation. RESULTS Lower glutathione, a measure of increased oxidative stress was associated with impaired microvascular function [CFVR (r=0.39, p=0.01) and HMR (r=-0.43, p=0.004)], greater plaque burden (r=-0.32, p=0.03) and necrotic core (r=-0.39, p=0.008). Similarly, higher cystine/glutathione ratio was associated with impaired microvascular function [CFVR (r=-0.29, p=0.04)] and greater necrotic core (r=0.37, p=0.01). In comparison, higher hs-CRP was associated only with greater necrotic core (r=0.45, p=0.003). After multivariate adjustment for age, gender, hypertension, diabetes, acute coronary syndrome presentation, body mass index, tobacco abuse, statin use and hs-CRP, glutathione remained an independent predictor of CFVR, HMR and necrotic core (p<0.05). CONCLUSIONS Lower plasma glutathione level a measure of increased oxidative stress, was an independent predictor of impaired coronary microvascular function and plaque necrotic core.

Usefulness of Serum High-Density Lipoprotein Cholesterol Level as an Independent Predictor of One-Year Mortality After Percutaneous Coronary Interventions

Low levels of high-density lipoprotein (HDL) cholesterol are a marker of coronary artery disease progression and are associated with cardiovascular events. However, whether low HDL cholesterol is a useful prognostic indicator after percutaneous coronary intervention (PCI) is not known. In a sample of 4,088 patients who underwent PCI we evaluated 1-year mortality and repeat revascularization as a function of baseline HDL levels classified into approximate quartiles of very low (<35 mg/dl), low (35 to 40 mg/dl), medium (41 to 47 mg/dl) and high (48 to 120 mg/dl) HDL cholesterol. Decreasing levels of HDL cholesterol were associated with younger age, male gender, smoking, diabetes mellitus, and a history of bypass surgery (p <0.0001 for all). One-year mortality and coronary revascularization were significantly higher in the very low HDL cholesterol group compared with the other groups (very low HDL cholesterol 6.5% and 25.4%, respectively; low HDL cholesterol 3.1% and 20.8%; medium HDL cholesterol 4.3% and 22.7%; high HDL cholesterol 3.1% and 20.6%, p = 0.0001 and p = 0.007). One-year mortality was significantly higher in men with an HDL cholesterol level <33 mg/dL and in women with an HDL cholesterol level <38 mg/dL. In multivariable analysis, very low HDL was associated with nearly twofold the risk of death after adjusting for other independent predictors of outcome. In conclusion, in patients with coronary artery disease undergoing PCI, a baseline HDL cholesterol level <35 mg/dl is an important prognostic indicator. Baseline HDL cholesterol levels <33 mg/dl for men and <38 mg/dl were associated with higher one-year mortality after PCI.

Localization of culprit lesions in coronary arteries of patients with ST-segment elevation myocardial infarctions: Relation to bifurcations and curvatures

BACKGROUND Although culprit lesions in ST-segment elevation myocardial infarction (STEMI) cluster in the proximal coronary arteries, their relationship to bifurcations and curvatures, where blood flow is disturbed, is unknown. We hypothesized that (a) culprit lesions localize to disturbed flow distal to bifurcations and curvatures and (b) the distribution of culprit lesions in the left (LCA) and right coronary arteries (RCA) and resulting infarct size are related to the location of bifurcations and curvatures. METHODS Emory Universitys contribution to the National Cardiovascular Data Registry was queried for STEMIs. Using quantitative coronary angiography, the distances from the vessel ostium, major bifurcations, and major curvatures to the culprit lesion were measured in 385 patients. RESULTS Culprit lesions were located within 20 mm of a bifurcation in 79% of patients and closer to the bifurcation in the LCA compared with the RCA (7.4 ± 7.3 vs 17.7 ± 14.8 mm, P < .0001). Of RCA culprit lesions, 45% were located within 20 mm of a major curvature. Compared with those in the RCA, culprit lesions in the LCA were located more proximally (24.4 ± 16.5 vs 44.7 ± 28.8 mm, P = .0003) and were associated with larger myocardial infarctions as assessed by peak creatine kinase-MB (208 ± 222 vs 140 ± 153 ng/dL, P = .001) and troponin I (59 ± 62 vs 40 ± 35 ng/dL, P = .0006) and with higher in-hospital mortality (5.2% vs 1.1%, P = .04). CONCLUSIONS In patients with STEMI, culprit lesions are frequently located immediately distal to bifurcations and in proximity to major curvatures where disturbed flow is known to occur. This supports the role of wall shear stress in the pathogenesis of STEMI.

Massive Penny Ingestion: The Loot with Local and Systemic Effects

A 57-year-old schizophrenic woman presented with lethargy, nausea, vomiting, and anorexia after coin ingestion. She was found to have multiple organ dysfunction manifested as hepatitis, pancreatitis, severe anemia with markedly depressed bone marrow response, extravascular hemolysis, and acute renal failure. Prolonged exposure to zinc from massive coin ingestion was responsible. Zinc poisoning is an unusual consequence of coin ingestion in the adult human literature. A detailed discussion on zinc poisoning, as well as the pitfalls in radiological diagnosis of massive coin ingestion, is presented.

Pseudo-Wellens’ syndrome after crack cocaine use

A 41-year-old man without a history of coronary artery disease presented with cardiac chest pain 3 h in duration. The initial electrocardiogram (Figure 1) revealed T wave inversions in leads V1 to V4 without loss of R wave or ST segment changes. He admitted to crack cocaine use all day. The physical examination was within normal limits. His urine drug screen was positive for cocaine. Urgent cardiac catheterization revealed normal coronary arteries and an ejection fraction of 60%. Cardiac enzymes were negative. Twenty-four hours later, a repeat electrocardiogram (Figure 2) showed reversal of T wave inversions. It is important for cardiologists to keep in mind that Wellens’ syndrome can be mimicked by cocaine-induced vasospasm of the proximal left anterior descending artery, because administration of beta-blockers in such circumstances can prove to be disastrous. Figure 1) Initial electrocardiogram on presentation revealing T wave inversion in leads V1 to V4, called Wellens’ T waves, which signified cocaine-induced vasospasm of the left anterior descending artery Figure 2) Repeat electrocardiogram showing resolution of Wellens’ T waves, which signfied resolution of vasospasm