Experimental Animal Models Evaluating the Causal Role of Lipoprotein(a) in Atherosclerosis and Aortic Stenosis.

Lipoprotein(a) [Lp(a)], comprised of apolipoprotein(a) [apo(a)] and a low-density lipoprotein-like particle, is a genetically determined, causal risk factor for cardiovascular disease and calcific aortic valve stenosis. Lp(a) is the major plasma lipoprotein carrier of oxidized phospholipids, is pro-inflammatory, inhibits plasminogen activation, and promotes smooth muscle cell proliferation, as defined mostly through in vitro studies. Although Lp(a) is not expressed in commonly studied laboratory animals, mouse and rabbit models transgenic for Lp(a) and apo(a) have been developed to address their pathogenicity in vivo. These models have provided significant insights into the pathophysiology of Lp(a), particularly in understanding the mechanisms of Lp(a) in mediating atherosclerosis. Studies in Lp(a)-transgenic mouse models have demonstrated that apo(a) is retained in atheromas and suggest that it promotes fatty streak formation. Furthermore, rabbit models have shown that Lp(a) promotes atherosclerosis and vascular calcification. However, many of these models have limitations. Mouse models need to be transgenic for both apo(a) and human apolipoprotein B-100 since apo(a) does not covalently associated with mouse apoB to form Lp(a). In established mouse and rabbit models of atherosclerosis, Lp(a) levels are low, generally < 20 mg/dL, which is considered to be within the normal range in humans. Furthermore, only one apo(a) isoform can be expressed in a given model whereas over 40 isoforms exist in humans. Mouse models should also ideally be studied in an LDL receptor negative background for atherosclerosis studies, as mice don't develop sufficiently elevated plasma cholesterol to study atherosclerosis in detail. With recent data that cardiovascular disease and calcific aortic valve stenosis is causally mediated by the LPA gene, development of optimized Lp(a)-transgenic animal models will provide an opportunity to further understand the mechanistic role of Lp(a) in atherosclerosis and aortic stenosis and provide a platform to test novel therapies for cardiovascular disease.

Role of Quantitation of Saline Bubble Studies in Patients with Liver Cirrhosis.

OBJECTIVE: Microbubble contrast echocardiography with a late positive signal enables the detection of intrapulmonary vascular dilation, including hepatopulmonary syndrome, in patients with end-stage liver disease. We assessed the relationship between the severity of bubble study and clinical outcome. METHODS: We retrospectively analyzed 163 consecutive patients with liver cirrhosis who underwent an echocardiogram with bubble study from 2018 to 2021. Patients who were diagnosed with a late positive signal were divided into three groups: grade 1 (1-9 bubbles), grade 2 (10-30 bubbles) and grade 3 (>30 bubbles). RESULTS: Fifty-six percent of the patients had a late positive bubble study (grade 1: 31%, grade 2: 23%, grade 3: 46%). Patients with grade 3 had a significantly higher international normalized ratio, model for end-stage liver disease score and Child-Pugh score and a lower peripheral oxygen saturation compared with patients with a negative study. In patients undergoing liver transplant (LT), survival rates were similar among the groups (3-mo: >87%, 1-y: >87%, 2-y: >83%). However, survival rate was lower in grade 3 patients without LT (3-mo: 81%, 1-y: 64%, 2-y: 39%). CONCLUSION: Patients with grade 3 had much worse mortality without LT compared with other groups. However, after LT, all grades had equal survival. Therefore, patients with grade 3 may be considered as higher priority for LT.

Established and emerging roles for ultrasound enhancing agents (contrast echocardiography).

The ability to opacify the left ventricle and delineate the endocardium after intravenous injection of microbubble ultrasound enhancing agents is of established value to quantify volumes and function in suboptimal unenhanced images, particularly in stress echocardiograms. However, applications other than quantitation of left ventricle structure and function exist for contrast enhanced left ventricular opacification. Contrast agents enable recording of Doppler velocity signals in patients with poor ultrasound transmission, providing estimates of aortic stenosis gradient and pulmonary artery pressures. Contrast echo is of value in detecting apical hypertrophic cardiomyopathy and accompanying apical aneurysms. Most importantly, ultrasound enhancing agents can identify apical and left atrial masses when they cannot be visualized in unenhanced images, and can distinguish thrombi from tumors by visualizing the vascularity inherent in tumors. Contrast agents distinguish trabecular from compacted myocardium in noncompaction syndrome, and hypertrabeculation with other abnormal conditions. A major potential application of ultrasound enhancing agents is myocardial opacification, which can assist in identifying nonviable myocardium. Also, the delayed reappearance of myocardial perfusion after microbubble destruction identifies impaired contrary flow and can diagnose coronary stenosis. Innovative applications of ultrasound contrast agents currently under investigation, include visualizing the vaso vasorum to identify plaques and assess their vulnerability, and theranostic agents to deliver drugs and biologists and to assist in sonothrombolysis. It is anticipated that the role of ultrasound contrast agents will continue to increase in the future.

Trends in testing and prevalence of elevated Lp(a) among patients with aortic valve stenosis.

BACKGROUND AND AIMS: Lipoprotein(a) [Lp(a)] is causally associated with aortic valve stenosis (AS) but Lp(a) testing among AS patients is not broadly incorporated into clinical practice. We evaluated trends in Lp(a) testing in an academic medical center. METHODS: Educational efforts and adding Lp(a) to the lipid panel on the electronic medical record (EMR) and pre-procedure order sets were used to increase awareness of Lp(a) as a risk factor in AS. Medical records at University of California San Diego Health (UCSDH) were analyzed from 2010 to 2020 to define the yearly frequency of first time Lp(a) testing in patients with diagnosis codes for AS or undergoing transcatheter aortic valve replacement (TAVR). RESULTS: Lp(a) testing for any indication increased over 5-fold from 2010 to 2020. A total of 3808 patients had a diagnosis of AS and 417 patients had TAVR. Lp(a) levels >30 mg/dL were present in 37% of AS and 35% of TAVR patients. The rates of Lp(a) testing in AS and TAVR were 14.0% and 65.7%, respectively. In AS, Lp(a) testing increased over time from 8.5% in 2010, peaking at 24.2% in 2017, and declining to 13.9% in 2020 (p < 0.001 for trend). Following implementation of EMR order-sets in 2016, Lp(a) testing in TAVR cases increased to a peak of 88.5% in 2018. CONCLUSIONS: Elevated Lp(a) is prevalent in AS and TAVR patients. Implementation of educational efforts and practice pathways resulted in increased Lp(a) testing in patients with AS. This study represents a paradigm that may allow increased global awareness of Lp(a) as a risk factor for AS.

Optimal Quantification of Functional Mitral Regurgitation: Comparison of Volumetric and Proximal Isovelocity Surface Area Methods to Predict Outcome.

Background Effective orifice area (EOA) ≥0.2 cm2 or regurgitant volume (Rvol) ≥30 mL predicts prognostic significance in functional mitral regurgitation (FMR). Both volumetric and proximal isovelocity surface area (PISA) methods enable calculation of these metrics. To determine their clinical value, we compared EOA and Rvol derived by volumetric and PISA quantitation upon outcome of patients with FMR. Methods and Results We examined the outcome of patients with left ventricular ejection fraction <35% and moderate to severe FMR. All had a complete echocardiogram including EOA and Rvol by both standard PISA and volumetric quantitation using total stroke volume calculated by left ventricular end-diastolic volume×left ventricular ejection fraction and forward flow by Doppler method: EOA=Rvol/mitral regurgitation velocity time integral. Primary outcome was all-cause mortality or heart transplantation. We examined 177 patients: mean left ventricular ejection fraction 25.2% and 34.5% with ischemic cardiomyopathy. Echo measurements were greater by PISA than volumetric quantitation: EOA (0.18 versus 0.11 cm2), Rvol (24.7 versus 16.9 mL), and regurgitant fraction (61 versus 37 %) respectively (all P value <0.001). During 3.6±2.3 years' follow-up, patients with EOA ≥0.2 cm2 or Rvol ≥30 mL had a worse outcome than those with EOA <0.2 cm2 or Rvol <30 mL only by volumetric (log rank P=0.003 and 0.004) but not PISA quantitation (log rank P=0.984 and 0.544), respectively. Conclusions Volumetric and PISA methods yield different measurements of EOA and Rvol in FMR; volumetric values exhibit greater prognostic significance. The echo method of quantifying FMR may affect the management of this disorder.

Clinical and Echocardiographic Predictors of Reduced Survival in Patient with Functional Mitral Regurgitation.

Functional mitral regurgitation (FMR) is associated with a poor outcome in patients with reduced left ventricular ejection fraction (LVEF). Two recent studies of percutaneous mitral valvular repair therapy reported disparate results, likely due in part to variable risk among FMR patients. The aim of this study is to define echocardiographic factors of prognostic significance in FMR patients, and particularly to compare ischemic and nonischemic FMR. We followed three hundred sixteen consecutive patients (age 60 ± 14 years, men 70%) with FMR and LVEF ≤ 35% between January 2010 and December 2015 (mean follow-up 3.7 years). Patients were categorized into ischemic (39.6%) and nonischemic (60.4%). MR was graded according to the American Society of Echocardiography guidelines. Although echo findings were similar between ischemic and nonischemic patient, the incidence of death, heart transplantation (HT), or LVAD implantation was higher in ischemic than in nonischemic patients (Log rank p = 0.001). In age and gender adjusted multivariate (11 variables) Cox regression analysis, left atrium volume index (LAVI) was associated with death, HT, or LVAD with hazard ratio of 2.1 for patients with FMR (p = 0.003). LAVI greater than 48.7 mL/m2 predicts adverse outcome in both nonischemic and ischemic FMR (AUC 0.62, p < 0.001). Combined ischemic FMR with LAVI ≥ 48.7 mL/m2 had the highest incident rate of all groups. In conclusion, despite similar LV function and MR severity, ischemic FMR patients had higher mortality than nonischemic patients. Of all echocardiographic parameters, an LAVI ≥ 48.7 mL/m2 predicted adverse clinical outcome.

Persistent Value of the Stethoscope in the Age of COVID-19.

The stethoscope has long been at the center of patient care, as well as a symbol of the physician-patient relationship. While advancements in other diagnostic modalities have allowed for more efficient and accurate diagnosis, the stethoscope has evolved in parallel to address the needs of the modern era of medicine. These advancements include sound visualization, ambient noise reduction/cancellation, Bluetooth (Bluetooth SIG Inc, Kirkland, Wash) transmission, and computer algorithm diagnostic support. However, despite these advancements, the ever-changing climate of infection prevention, especially in the wake of the COVID-19 pandemic, has led many to question the stethoscope as a vector for infectious diseases. Stethoscopes have been reported to harbor bacteria with contamination levels comparable with a physician's hand. Although disinfection is recommended, stethoscope hygiene compliance remains low. In addition, disinfectants may not be completely effective in eliminating microorganisms. Despite these risks, the growing technological integration with the stethoscope continues to make it a highly valuable tool. Rather than casting our valuable tool and symbol of medicine aside, we must create and implement an effective method of stethoscope hygiene to keep patients safe.

Development of a Translatable Ultrasound Molecular Imaging Agent for Inflammation.

This study details the development, characterization and non-clinical efficacy of an ultrasound molecular imaging agent intended for molecular imaging of P-selectin in humans. A targeting ligand based on a recently discovered human selectin ligand was manufactured as fusion protein, and activity for human and mouse P- and E-selectin was evaluated by functional immunoassay. The targeting ligand was covalently conjugated to a lipophilic anchor inserted into a phospholipid microbubble shell. Three lots of the targeted microbubble drug product, TS-07-009, were produced, and assays for size distribution, zeta potential and morphology were established. The suitability of TS-07-009 as a molecular imaging agent was evaluated in vitro in a flow-based adhesion assay and in vivo using a canine model of transient myocardial ischemia. Selectivity for P-selectin over E-selectin was observed in both the human and murine systems. Contrast agent adhesion increased with P-selectin concentration in a dynamic adhesion assay. Significant contrast enhancement was observed on ultrasound imaging with TS-07-009 in post-ischemic canine myocardium at 30 or 90 min of re-perfusion. Negligible enhancement was observed in resting (no prior ischemia) hearts or with a control microbubble 90 min after ischemia. The microbubble contrast agent described here exhibits physiochemical properties and in vivo behavior suitable for development as a clinical imaging agent.

Lipoprotein(a) in Patients Undergoing Transcatheter Aortic Valve Replacement.

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for calcific aortic valve stenosis (CAVS) for which transcatheter aortic valve replacement (TAVR) is increasingly utilized as treatment. We evaluated the effect of a program to increase testing of and define the prevalence of elevated Lp(a) among patients undergoing TAVR. Educational efforts and incorporation of a "check-box" Lp(a) order to the preoperative TAVR order set were instituted. Retrospective chart review was performed in 229 patients requiring TAVR between May 2013 and September 2018. Of these patients, 57% had an Lp(a) level measured; testing rates increased from 0% in 2013 to 96% in 2018. Lipoprotein(a) testing occurred in 11% of patients before and in 80% of patients after the "check-box" order set ( P < .001). The prevalence of elevated Lp(a) (≥30 mg/dL) was 35%; these patients had a higher incidence of coronary artery disease requiring revascularization compared with patients with normal Lp(a) (65% vs 47%; P = .047). Patients with Lp(a) ≥30 mg/dL also had higher incidence of paravalvular leak compared with those with normal Lp(a) (13% vs 4%; P = .04). This study defines the prevalence of elevated Lp(a) in advanced stages of CAVS and provides a practice pathway to assess procedural complications and long-term outcomes of TAVR in patients with elevated Lp(a) levels.

Cross-sectional study of endothelial function in HIV-infected patients in Brazil.

Antiretroviral therapy (ART) in HIV-infected patients has been associated with an increased risk of cardiovascular disease. This study evaluates vascular endothelial dysfunction of the peripheral circulation in Brazilian HIV-infected subjects on ART or naive to ART compared to a control group matched for age and body mass index (BMI). We performed a cross-sectional comparative study to measure postischemic peak flow-mediated dilation (FMD) of the brachial artery and the response to glyceryl trinitrate (GTN) in HIV-infected patients and healthy controls in Salvador, Bahia, Brazil. Endothelial vasomotor function was evaluated by assessing brachial artery FMD. Forty-four HIV-infected individuals (33 ARV treated and 11 ART naive) were compared to 25 healthy controls matched for age and BMI. FMD % was significantly lower for the ART-experienced patients compared to the ART-naive patients and was also significantly different from controls (ART experienced 8.2 +/- 6.0% vs. 19.3 +/- 4.8% vs. 23.3 +/- 6.1%), respectively (p < 0.0001). The cholesterol, triglyceride, and ALT levels were significantly higher in the ART-experienced group compared to the ART-naive and control subjects (p < 0.028); however, linear regression analysis revealed a statistically significant association of endothelial dysfunction as a dependent variable only with ARV treatment in HIV-infected subjects (p = 0.03). The association of endothelial dysfunction with ARV therapy in HIV-infected patients was independent of protease inhibitor-containing regimens or dyslipidemia. This dysfunction may contribute to the risk for HIV-associated atherosclerosis.

The Prevalence of Lipoprotein(a) Measurement and Degree of Elevation Among 2710 Patients With Calcific Aortic Valve Stenosis in an Academic Echocardiography Laboratory Setting.

Lipoprotein(a; Lp[a]) and its associated oxidized phospholipids are causal, genetic risk factors for calcific aortic valve stenosis (CAVS). We determined the prevalence of Lp(a) measurement among 2710 patients with CAVS and 1369 control patients (∼50% of study group) without CAVS with an echocardiogram between January 2010 and February 2016 in an academic echocardiography laboratory. Lipoprotein(a) measurements were performed at a referral laboratory using an isoform-independent assay. The prevalence of any Lp(a) measurement was 4.6% (124 of the 2710) in patients with CAVS and 3.1% (42 of the 1369) in the control group ( P = .021). In patients with CAVS, mean (standard deviation) Lp(a) levels were 38 (54) mg/dL and median (interquartile range) Lp(a) levels were 14 (6-48) mg/dL. Of the 124 patients with CAVS having Lp(a) measurements, 83 (66.9%) had Lp(a) <30 mg/dL and 41 (33.1%) had Lp(a) ≥30 mg/dL. This study reflects low physician testing of Lp(a) levels in CAVS. Given the role of Lp(a) as a causal risk factor for CAVS, and the ongoing development of therapies to normalize Lp(a) levels, our results suggest that Lp(a) measurements in CAVS should be more widely obtained in clinical practice.

Endothelial function and cardiovascular diseases in HIV infected patient.

The HIV epidemic has dramatically changed the paradigm for the development of drug therapy in the last 15 years. The goal is now not only to provide an effective reduction of plasma viremia , but also to reconstitute the immune deficiency due to the progression of the disease. Significant problems with the metabolism of sugars and lipids lead to the appearance of well-documented disorders such as insulin resistance, abnormalities in lipid metabolism and lipodystrophy in those patients on prolonged therapy with antiretrovirals. The question of whether or not HAART-associated lipid disorders contribute to the premature development of coronary artery disease is of major importance for the HIV community. Endothelial injury is associated with disease-related biochemical abnormalities that are implicated in HIV pathogenesis. The exploration of endothelial function began in the early 1980s at the start of the epidemic. The study of endothelial function in HIV infection and its modifications by HAART is an exciting new field in clinical research; in this review the available information on cardiovascular diseases associated with HIV infection and its treatment are discussed.

Visualization of risk-area myocardium as a high-intensity, hyperenhanced "hot spot" by myocardial contrast echocardiography following coronary reperfusion: quantitative analysis.

OBJECTIVES: We examined whether delayed post-injection imaging of a new ultrasound contrast agent (BR-14) could produce prolonged opacification and hyperenhancement of myocardium subjected to coronary occlusion/reperfusion. BACKGROUND: We hypothesized that ultrasound exposure destroyed BR-14 and eliminated visualization of sustained myocardial opacification from retained microbubbles. METHODS: We studied eight open-chest dogs with 3 h of left anterior descending coronary artery (LAD) occlusion followed by 3 h of reperfusion. Myocardial contrast echocardiography (MCE) was performed before occlusion and 120 min after the onset of both occlusion and reperfusion. Ultrasound imaging was initiated 15 min after injection. Myocardial blood flow (MBF) was assessed by microspheres. RESULTS: Pre-occlusion images revealed uniform opacification of left ventricular myocardium greater than that of the cavity, with a mean intensity of the LAD bed of 8.66 +/- 1.38 dB. During occlusion, MCE resulted in the appearance of a perfusion defect in the LAD risk area (intensity 2.08 +/- 1.10 dB). After 120 min of reperfusion, the LAD risk-area myocardium manifested dense opacification of a higher intensity ("hot spot") than baseline (13.7 vs. 8.7 dB), but with reduced MBF consistent with accumulation of a high concentration of microbubbles. Increased MCE intensity was associated with a greater myeloperoxidase score. CONCLUSIONS: These data establish that contrast opacification by BR-14 may be selectively retained within the perfusion bed of a coronary artery subjected to occlusion/reperfusion. Such opacification exhibits defects with occlusion, manifests hyperenhanced intensity (hot spot) with reperfusion, is associated with the level of myeloperoxidase activity, and conforms to the area of myocardium subjected to altered flow.

Comparison of dobutamine stress echocardiography with and without real-time perfusion imaging for detection of coronary artery disease.

In a pilot study of 27 patients, those who presented with chest pain underwent 2 dobutamine stress echocardiographic studies, 1 with high mechanical index harmonic imaging to analyze wall motion without contrast and 1 with real-time low mechanical index perfusion imaging with intravenous Optison to assess myocardial perfusion and wall motion. All patients then underwent quantitative coronary angiography. Two independent reviewers demonstrated an improvement in sensitivity when analyzing myocardial perfusion. In the 21 patients who had significant coronary stenoses, 14 had abnormal myocardial perfusion detected at peak stress and 7 had abnormal wall motion detected by standard dobutamine stress echocardiography. There was decreased specificity with perfusion imaging by 1 reviewer. The addition of real-time perfusion imaging after intravenous contrast during dobutamine stress echocardiography has the potential to improve detection of coronary artery disease.

Cardiovascular effects of antiretroviral therapy and noninvasive assessments of cardiovascular disease in HIV infection.

The heart is frequently affected in patients with the acquired immune deficiency syndrome (AIDS). Although the introduction of potent antiretroviral therapy (ART) has produced a sharp decline in mortality and morbidity in HIV-infected patients, the use of ART is associated with the development of peripheral insulin resistance, dyslipidemia, and lipodystrophy. These abnormalities are also associated with coronary artery disease, and numerous reports of myo-cardial infarction in young HIV-infected patients have raised concerns of pre-mature coronary disease in this population. A comprehensive review of the epidemiology of coronary artery disease is given. In recent years, several non-invasive methods to detect early development of atherosclerosis have been evaluated. Two noninvasive techniques using ultrasound have emerged as valid methods to detect early development of atherosclerosis: intima-media thickness and endothelial dysfunction assessed by the measurement of flow-mediated brachial artery dilatation. Multicenter, randomized trials using either technique may provide more information about whether HIV infection alone, long-term HAART use, or both may increase the risks of or accelerate coronary disease in HIV-infected patients.

Effect of microbubble fragility on transit rate measurement by contrast echography.

We sought to propose a simplified method to measure flow velocity based on ultrasonic microbubble destruction, and investigated the effect of microbubble shell fragility on such measurement. Acoustic density (AD) from the second harmonic short axis image of flow was obtained at variable velocities (2 to 73 mm/s) in an in vitro model during long (1000 ms) and short (33 ms) interval ultrasound (US) pulsing, allowing complete and partial microbubble replenishment between pulses, respectively. Microbubbles with shell elastic modulus of 0.4 MPa and 16 MPa were tested. By shortening pulsing interval, AD diminished gradually, rather than abruptly, to a plateau level for both microbubbles. The extent of AD decay was greater for the fragile than the strong microbubbles. A linear relationship existed between the magnitude of AD decay and flow velocity only in the higher and lower velocity range for the fragile and the strong microbubbles, respectively. Thus, difference in contrast intensities during long and short pulsing intervals, respectively, allowing complete and partial replenishment may provide for velocity measurement, in which choice of optimal microbubble fragility for the range of velocity to measure may increase the accuracy.

Mitochondrial DNA variation and changes in adiponectin and endothelial function in HIV-infected adults after antiretroviral therapy initiation.

Studies in persons of European descent have suggested that mitochondrial DNA (mtDNA) haplogroups influence antiretroviral therapy (ART) toxicity. We explored associations between mtDNA variants and changes in endothelial function and biomarkers among non-Hispanic white, ART-naive subjects starting ART. A5152s was a substudy of A5142, a randomized trial of initial class-sparing ART regimens that included efavirenz or lopinavir/ritonavir with nucleoside reverse transcriptase inhibitors (NRTIs), or both without NRTIs. Brachial artery flow-mediated dilation (FMD) and cardiovascular biomarker assessments were performed at baseline and at weeks 4 and 24. Ten haplogroup-defining mtDNA polymorphisms were determined. FMD and biomarker changes from baseline to week 24 by mtDNA variant were assessed using Wilcoxon rank-sum tests. Thirty-nine non-Hispanic white participants had DNA and 24-week data. The nonsynonymous m.10398A>G mtDNA polymorphism (N=8) was associated with higher median baseline adiponectin (5.0 vs. 4.2 µg/ml; p=0.003), greater absolute (-1.9 vs. -0.2 µg/ml) and relative (-33% vs. -3%) adiponectin decreases (p<0.001 for both), and lower week 24 brachial artery FMD (3.6% vs. 5.4%; p=0.04). Individual mtDNA haplogroups, including haplogroups H (N=13) and U (N=6), were not associated with adiponectin or FMD changes. In this small pilot study, adiponectin and brachial artery FMD on ART differed in non-Hispanic whites with a nonsynonymous mtDNA variant associated with several human diseases. These preliminary findings support the hypothesis that mtDNA variation influences metabolic ART effects. Validation studies in larger populations and in different racial/ethnic groups that include m.10398G carriers are needed.