Significance of Coronary Artery Calcium Found on Non-Electrocardiogram-Gated Computed Tomography During Preoperative Evaluation for Liver Transplant

Coronary artery calcium assessment on non-gated chest CT to optimize pre-operative cardiac screening in liver transplantation

BACKGROUND

Guidelines recommend standard pre-operative cardiac screening in all liver transplantation (LT) recipients, despite the relatively low prevalence of obstructive coronary artery disease. Most LT recipients often have non-gated computed tomography (CT) performed of the chest and abdomen. This study evaluated the ability of coronary artery calcification (CAC) assessment on consecutively available scans, to identify a selection of low-risk patients, in whom further cardiac imaging can be safely withheld.

METHODS

LT recipients with prior non-gated CT chest-abdomen were included. CAC was visually scored on a semi-quantitative ordinal scale. Stress myocardial perfusion, coronary CT angiography (CCTA) and invasive coronary angiography (ICA) were used as golden standard. The sensitivity and specificity of CAC to exclude and predict obstructive CAD were assessed. In addition, peri- and postoperative mortality and cardiac events were analyzed.

RESULTS

149 LT recipients (ranged 31-71 years) were included. In 75% of patients, no CAC and mild CAC could rule out obstructive CAD on CCTA and ICA with 100% certainty. The threshold of mild CAC had a sensitivity of 100% for both CCTA and ICA and a specificity of 91% and 68%, respectively. None of the patients with no or mild calcifications experienced peri- and post-operative cardiac events or died of cardiac causes.

CONCLUSION

Visual evaluation of CAC on prior non-gated CT can accurately and safely exclude obstructive CAD in LT recipients. Incorporation of these already available data can optimize cardiac screening, by safely withholding or correctly allocating dedicated cardiac imaging in LT recipients. Thereby, reducing patients' test burden and save health care expenses.

Prevalence and clinical implications of coronary artery calcium scoring on non-gated thoracic computed tomography: a systematic review and meta-analysis

OBJECTIVES

Coronary artery calcifications (CACs) indicate the presence of coronary artery disease. CAC can be found on thoracic computed tomography (CT) conducted for non-cardiac reasons. This systematic review and meta-analysis of non-gated thoracic CT aims to assess the clinical impact and prevalence of CAC.

METHODS

Online databases were searched for articles assessing prevalence, demographic characteristics, accuracy and prognosis of incidental CAC on non-gated thoracic CT. Meta-analysis was performed using a random effects model.

RESULTS

A total of 108 studies (113,406 patients) were included (38% female). Prevalence of CAC ranged from 2.7 to 100% (pooled prevalence 52%, 95% confidence interval [CI] 46-58%). Patients with CAC were older (pooled standardised mean difference 0.88, 95% CI 0.65-1.11, p < 0.001), and more likely to be male (pooled odds ratio [OR] 1.95, 95% CI 1.55-2.45, p < 0.001), with diabetes (pooled OR 2.63, 95% CI 1.95-3.54, p < 0.001), hypercholesterolaemia (pooled OR 2.28, 95% CI 1.33-3.93, p < 0.01) and hypertension (pooled OR 3.89, 95% CI 2.26-6.70, p < 0.001), but not higher body mass index or smoking. Non-gated CT assessment of CAC had excellent agreement with electrocardiogram-gated CT (pooled correlation coefficient 0.96, 95% CI 0.92-0.98, p < 0.001). In 51,582 patients, followed-up for 51.6 ± 27.4 months, patients with CAC had increased all cause mortality (pooled relative risk [RR] 2.13, 95% CI 1.57-2.90, p = 0.004) and major adverse cardiovascular events (pooled RR 2.91, 95% CI 2.26-3.93, p < 0.001). When CAC was present on CT, it was reported in between 18.6% and 93% of reports.

CONCLUSION

CAC is a common, but underreported, finding on non-gated CT with important prognostic implications.

CLINICAL RELEVANCE STATEMENT

Coronary artery calcium is an important prognostic indicator of cardiovascular disease. It can be assessed on non-gated thoracic CT and is a commonly underreported finding. This represents a significant population where there is a potential missed opportunity for lifestyle modification recommendations and preventative therapies. This study aims to highlight the importance of reporting incidental coronary artery calcium on non-gated thoracic CT.

KEY POINTS

• Coronary artery calcification is a common finding on non-gated thoracic CT and can be reliably identified compared to gated-CT. • Coronary artery calcification on thoracic CT is associated with an increased risk of all cause mortality and major adverse cardiovascsular events. • Coronary artery calcification is frequently not reported on non-gated thoracic CT.

Evaluation of recipients with significant comorbidity - Patients with cardiovascular disease

Liver transplant(ation) (LT) is the most effective treatment for patients with decompensated liver disease. The increasing prevalence of obesity and type 2 diabetes and the growing number of patients with non-alcoholic fatty liver disease being evaluated for LT, have resulted in a greater proportion of LT candidates presenting with a higher risk of cardiovascular disease. As cardiovascular disease is a major cause of morbidity and mortality after LT, a thorough cardiovascular evaluation pre-LT is crucial. In this review, we discuss the latest evidence on the cardiovascular evaluation of LT candidates and we focus on the most prevalent conditions, namely ischaemic heart disease, atrial fibrillation and other arrhythmias, valvular heart disease, and cardiomyopathies. LT candidates undergo an electrocardiogram, a resting transthoracic echocardiography and an assessment of their cardiopulmonary functional ability as part of their standardised pre-LT work-up. Further diagnostic work-up is undertaken based on the results of the baseline evaluation and may include a coronary computed tomography angiography in patients with cardiovascular risk factors. The evaluation of potential LT candidates for cardiovascular disease requires a multidisciplinary approach, with input from anaesthetists, cardiologists, hepatologists and transplant surgeons.

Assessment of Vascular and Valvular Calcification Improves Screening for Coronary Artery Disease Before Liver Transplantation

Coronary artery disease (CAD) is common in patients with cirrhosis who underwent orthotopic liver transplantation (OLT) evaluation and stress echocardiogram (echo) has a low sensitivity in these patients. This study aimed to assess the impact of vascular and valvular calcification on the ability to identify CAD before OLT. We performed a case-control study of 88 patients with and 97 without obstructive CAD who underwent OLT evaluation. All patients had a preoperative stress echo, abdominal computed tomography, and cardiac catheterization. A series of nested logistic regression models of CAD were fit by adding independent variables of vascular (including coronary) calcification, aortic and mitral valve calcification, age, gender, and history of diabetes mellitus requiring insulin to a baseline model of abnormal stress echo. Compared with stress echo alone, identification of the presence or absence of vascular and valvular calcification on routine preoperative computed tomography and echo improved the diagnostic performance for the detection of CAD based on coronary angiogram when combined with stress echo in patients with cirrhosis who underwent OLT evaluation (area under the curve 0.58 vs 0.73, p <0.001), which is even further improved when age, gender, and history of diabetes mellitus requiring insulin are considered (area under the curve 0.58 vs 0.80, p <0.001). Achieving target heart rate (p = 0.92) or rate-pressure product >25,000 (p = 0.63) did not improve the ability of stress echo to identify CAD. In conclusion, the use of abdominal vascular, coronary artery, and valvular calcification, along with stress echo, improves the ability to identify and rule out obstructive CAD before OLT compared with stress echo alone.

Liver transplantation for non-alcoholic fatty liver disease: indications and post-transplant management

Non-alcoholic fatty liver disease (NAFLD) is currently the fastest growing indication to liver transplantation (LT) in Western Countries, both for end stage liver disease and hepatocellular carcinoma. NAFLD/non-alcoholic steatohepatitis (NASH) is often expression of a systemic metabolic syndrome; therefore, NAFLD/NASH patients require a multidisciplinary approach for a proper pre-surgical evaluation, which is important to achieve a post-transplant outcome comparable to that of other indications to LT. NAFLD/NASH patients are also at higher risk of post-transplant cardiovascular events, diabetes, dyslipidemia, obesity, renal impairment and recurrent NASH. Lifestyle modifications, included diet and physical activity, are key to improve survival and quality of life after transplantation. A tailored immunosuppressive regimen may be proposed in selected patients. Development of new drugs for the treatment of recurrent NASH is awaited.

Emerging Evidence on Coronary Heart Disease Screening in Kidney and Liver Transplantation Candidates: A Scientific Statement From the American Heart Association: Endorsed by the American Society of Transplantation

Coronary heart disease is an important source of mortality and morbidity among kidney transplantation and liver transplantation candidates and recipients and is driven by traditional and nontraditional risk factors related to end-stage organ disease. In this scientific statement, we review evidence from the past decade related to coronary heart disease screening and management for kidney and liver transplantation candidates. Coronary heart disease screening in asymptomatic kidney and liver transplantation candidates has not been demonstrated to improve outcomes but is common in practice. Risk stratification algorithms based on the presence or absence of clinical risk factors and physical performance have been proposed, but a high proportion of candidates still meet criteria for screening tests. We suggest new approaches to pretransplantation evaluation grounded on the presence or absence of known coronary heart disease and cardiac symptoms and emphasize multidisciplinary engagement, including involvement of a dedicated cardiologist. Noninvasive functional screening methods such as stress echocardiography and myocardial perfusion scintigraphy have limited accuracy, and newer noninvasive modalities, especially cardiac computed tomography-based tests, are promising alternatives. Emerging evidence such as results of the 2020 International Study of Comparative Health Effectiveness With Medical and Invasive Approaches-Chronic Kidney Disease trial emphasizes the vital importance of guideline-directed medical therapy in managing diagnosed coronary heart disease and further questions the value of revascularization among asymptomatic kidney transplantation candidates. Optimizing strategies to disseminate and implement best practices for medical management in the broader end-stage organ disease population should be prioritized to improve cardiovascular outcomes in these populations.

Accurate measurement of coronary artery calcium in cancer patients using the CT component of PET/CT scans

OBJECTIVE

The aim of this study is to establish the correlation between a CAC score derived from the CT component of PET/CT scan (CAC-PET) using in-house software as compared to the conventional technique (CAC-Standard). In addition, the incidence of high CAC scores in asymptomatic cancer patients with low-to-intermediate cardiovascular risk will be determined.

METHODS

100 patients referred for oncologic PET/CT were prospectively recruited to have a conventional CAC score after their PET/CT. Patients with a history of cardiac disease were excluded. The nongated CT images from the PET/CT (CAC-PET) were analysed using validated in-house software with the results compared to those from gated CT analysed using the standard technique (CAC-Standard).

RESULTS

The correlation of CAC scores between the two scan types was moderate [slope, 0.95; R2 = 0.91; limits of agreement (LOA) = 0.29-5.65]. Using a conventional categorical analysis, there was complete agreement in 73% of patients with one category difference in the remainder. [interclass correlation (ICC) = 0.90; Cohen's kappa = 0.63]. In total 28% of these asymptomatic low-to-intermediate-risk cancer patients had CAC scores over 300.

CONCLUSION

Estimation of CAC from the CT component of PET/CT scans is a reliable method for the detection of significant CAC in cancer patients and correlates well with the standard method. This technique should permit the calculation of cardiovascular risk in cancer patients undergoing PET/CT without any additional radiation exposure. A significant number of asymptomatic low-to-intermediate-risk cancer patients were found to have a high risk of cardiovascular disease.

Diagnostic Yield of Coronary Angiography in Asymptomatic Orthotopic Liver Transplantation Candidates

BACKGROUND

The ideal cardiac risk stratification strategy for orthotopic liver transplantation (OLT) is unknown. Our institution performed coronary angiography for asymptomatic OLT candidates at high risk for CAD: ≥65 years of age, diabetic and ≥55 years of age or diagnosed ≥5 years, abnormal stress test, or at the discretion of the OLT committee.

METHODS

The analysis included 301 consecutive, asymptomatic OLT candidates who underwent coronary angiography. The primary outcome was the prevalence of obstructive CAD.

RESULTS

At 2-year follow-up, OLT was performed in 44.9%, and 42.2% died. The prevalence of obstructive CAD, involvement of the proximal or mid LAD, and 3-vessel CAD were 10.3%, 6.6%, and 0.7%, respectively. Percutaneous and surgical revascularization were performed in 7.0% and 1.3%, respectively. Stress test was performed in 54.8%. The sensitivity and specificity of stress testing were 0% and 87.1%, respectively. The negative and positive predictive values of stress testing were 91.4% and 0%, respectively. Chest computed tomography (CT) was performed in 83.1%. Moderate or severe coronary artery calcification (CAC) was present in 47.8%. The sensitivity and specificity of moderate or severe CAC were 88.9% and 57.3%, respectively. The negative and positive predictive values of moderate or severe CAC were 97.7% and 20.2%, respectively. Multivariate analysis demonstrated that CAC was an independent predictor of obstructive CAD (HR 10.7; 95% CI 3.2-37.9; p < 0.001).

CONCLUSIONS

The prevalence of obstructive CAD in asymptomatic OLT candidates at high risk was uncommon. Alternative diagnostic strategies may be preferred to coronary angiography.

Comparison of Coronary Artery Calcium Scoring with Dobutamine Stress Echo for Detection of Coronary Artery Disease Before Liver Transplantation

BACKGROUND Dobutamine stress echocardiography (DSE) is commonly used for cardiovascular assessment before orthotopic liver transplantation (OLT). The coronary artery calcium score (CACS) is a useful screening tool for coronary artery disease (CAD). We aimed to compare the sensitivity and specificity of DSE and CACS for CAD in OLT candidates. MATERIAL AND METHODS A total of 265 of the 1589 patients who underwent OLT at our center between 2008 and 2019 had preoperative coronary angiography (CAG). Of these, 173 had DSE and 133 had a CT scan suitable for CACS calculation within 1 year of OLT. Patients with a nondiagnostic DSE were excluded (n=100). Two reviewers evaluated CACS on CT scans. The sensitivity/specificity of DSE and CACS for detection of angiographically significant CAD were calculated for patients with both tests (n=36). A separate analysis compared the sensitivity/specificity of a diagnostic DSE (n=73) and CACS (n=133) against CAG for all patients with either test. RESULTS Sensitivity and specificity were 57.1% and 89.7%, respectively, for DSE, compared with 71.4% and 62.1% for CACS at ≥100 Agatston score. For the analysis of all patients with either test, the sensitivity/specificity of DSE for detection of CAD and CACS were 30.8% and 85.0% and 80.0% and 62.8%, respectively. On ROC analysis, CACS was a satisfactory predictor of obstructive CAD (AUC, 0.76±0.06, 95% CI, 0.66-0.87; P<0.001). CONCLUSIONS CACS may be an important tool for cardiovascular assessment in patients undergoing OLT. DSE was nondiagnostic in a large percentage of OLT candidates, limiting its use in this population.

Cardiac evaluation of the kidney or liver transplant candidate

PURPOSE OF REVIEW

As the field of transplant has advanced, cardiac events have become the leading cause of morbidity and mortality after liver and kidney transplantation ahead of graft failure and infection. This trend has been bolstered by the transplantation of older and sicker patients who have a higher burden of cardiovascular risk factors, accentuating the need to determine which patients should undergo more extensive cardiac evaluation prior to transplantation.

RECENT FINDINGS

Computed tomography coronary angiography with or without coronary artery calcium scoring is now preferred over stress imaging in most transplant candidates for assessment of coronary artery disease. Assessment of cardiac structure and function using transthoracic echocardiography with tissue doppler imaging and strain imaging is recommended, particularly in liver transplant candidates who are at high risk of cirrhotic cardiomyopathy, for which new diagnostic criteria were recently published in 2019.

SUMMARY

Cardiac evaluation of liver and kidney transplant candidates requires a global assessment for both short and long-term risk for cardiac events. Imaging of cardiac structure and function using transthoracic echocardiography with tissue doppler imaging and strain imaging is recommended. Risk stratification should consider both the anatomic and functional consequences of coronary artery disease in transplant candidates.

VIDEO ABSTRACT

http://links.lww.com/MOT/A27.

Preoperative Evaluation of Coronary Artery Disease in Liver Transplant Candidates: Many Unanswered Questions in Clinical Practice

Cardiovascular (CV) complications represent the first non-graft-related cause of death and the third overall cause of death among patients undergoing liver transplantation (LT). History of coronary artery disease is related to increased CV mortality following LT. Although it is of paramount importance to stratify CV risk in pre-LT patients, there is no consensus regarding the choice of the optimal non-invasive cardiac imaging test. Algorithms proposed by scientific associations include non-traditional risk factors, which are associated with increased cardiac risk profiles. Thus, an individualized pre-LT evaluation protocol should be followed. As the average age of patients undergoing LT and the number of candidates continue to rise, the “3 W” questions still remain unanswered, Who, Which and When? Who should be screened for coronary artery disease (CAD), which screening modality should be used and when should the asymptomatic waitlisted patients repeat cardiac evaluation? Prospective studies with large sample sizes are warranted to define an algorithm that can provide better risk stratification and more reliable survival prediction.

Pathogenesis of non-alcoholic fatty liver disease and implications on cardiovascular outcomes in liver transplantation

Along with the obesity epidemic there has been a major increase in non-alcoholic fatty liver disease (NAFLD) prevalence, paralleling a steady increase in cirrhosis of the liver and hepatocellular cancer (HCC) related to NAFLD. Currently, NAFLD (related HCC and cirrhosis) is the second most common cause for liver transplantation (LT) and it is projected to take the top spot in the next 3-5 years. Patients with NAFLD cirrhosis and HCC have a unique set of comorbidities which potentially increases their risk for cardiovascular disease (CVD) and mortality. However, a review of the published data in NAFLD patients who undergo LT, does not paint a clear picture. While CVD is the most common cause of non-graft related mortality over the long-term, the short and intermediate-term survival post LT in NAFLD cirrhosis appears to be on par with other etiologies when age and comorbidities are factored. The cardiovascular complications are increased in the immediate post-transplant period but there is a shift from ischemic complications to arrhythmias and heart failure (HF). NAFLD recurs in 80-100% patients and occurs de novo in about 50% after LT, potentially impacting their long-term morbidity and mortality. This review summarizes the available data on CVD in NAFLD patients before and after LT, explains what is currently known about the epidemiology and pathogenesis of CVD in NAFLD and posits strategies to improve wait-list and post-transplant survival.

Predictors of Myocardial Ischemia in Preoperative Oncology Patients Who Underwent Fluorodeoxyglucose-Positron Emission Tomography Study

Background:

Coronary artery calcification (CAC) can be visually estimated on computed tomography (CT) attenuation correction (CTAC) of positron emission tomography (PET). The visual estimation of CAC from CTAC scans performed for PET/CT is comparable to the standard CAC score scan. Myocardial perfusion imaging (MPI) with single-photon emission CT (SPECT) is commonly performed for risk stratification before oncologic surgery.

Objective:

We investigated the value of visual estimation of CAC from CTAC of PET/CT as well as other factors such as coronary artery disease (CAD) risk factors and type of cancer as predictors of MPI ischemia.

Methods:

Retrospectively, we identified 268 patients who underwent PET/CT and MPI for preoperative cardiac evaluation. Visual estimation of CAC was performed and classified into four categories.

Results:

The results of visual CAC were as follows: 47.8% – zero CAC, 32.8% – mild CAC, 14.2% – moderate CAC, and 5.2% – severe CAC. The majority of patients (85.8%) had normal MPI, whereas 14.2% were abnormal. There was a strong association between ischemia on MPI and CAC seen on CTAC (P < 0.01), dyslipidemia (P < 0.01), family history of CAD (P < 0.05), smoking (P < 0.01), and type of malignancy (P < 0.01).

Conclusion:

A strong association exists between visual estimation of CAC on CTAC and MPI. Zero is highly associated with normal MPI, but moderate-to-severe CAC is associated with abnormal MPI, in addition smoking, dyslipidemia, and certain cancer are associated with ischemic MPI; subsequently, preoperative cardiac testing is warranted in these subsets of patients.