The deleterious effects of arteriovenous fistula-creation on the cardiovascular system: a longitudinal magnetic resonance imaging study.

AIM: Arteriovenous fistula-formation remains critical for the provision of hemodialysis in end-stage renal failure patients. Its creation results in a significant increase in cardiac output, with resultant alterations in cardiac stroke volume, systemic blood flow, and vascular resistance. The impact of fistula-formation on cardiac and vascular structure and function has not yet been evaluated via "gold standard" imaging techniques in the modern era of end-stage renal failure care. METHODS: A total of 24 patients with stage 5 chronic kidney disease undergoing fistula-creation were studied in a single-arm pilot study. Cardiovascular magnetic resonance imaging was undertaken at baseline, and prior to and 6 months following fistula-creation. This gold standard imaging modality was used to evaluate, via standard brachial flow-mediated techniques, cardiac structure and function, aortic distensibility, and endothelial function. RESULTS: At follow up, left ventricular ejection fraction remained unchanged, while mean cardiac output increased by 25.0% (P<0.0001). Significant increases in left and right ventricular end-systolic volumes (21% [P=0.014] and 18% [P<0.01]), left and right atrial area (11% [P<0.01] and 9% [P<0.01]), and left ventricular mass were observed (12.7% increase) (P<0.01). Endothelial-dependent vasodilation was significantly decreased at follow up (9.0%±9% vs 3.0%±6%) (P=0.01). No significant change in aortic distensibility was identified. CONCLUSION: In patients with end-stage renal failure, fistula-formation is associated with an increase in cardiac output, dilation of all cardiac chambers and deterioration in endothelial function.

Beneficial cardiovascular remodeling following arterio-venous fistula ligation post-renal transplantation: a longitudinal magnetic resonance imaging study.

Despite improvements in survival following renal transplantation, high rates of cardiovascular morbidity and mortality remain. Persistence of arterio-venous fistulae (AVF) may contribute to maladaptive cardiovascular remodeling and poor health outcomes in this cohort. Utilizing recent advances in cardiovascular magnetic resonance imaging (CMR), we prospectively evaluated alterations in cardiac and vascular structure and function six months after elective ligation of AVF, following stable, successful renal transplantation. Eighteen subjects underwent CMR evaluation of cardiac structure and function, aortic distensibility and endothelial function prior to AVF ligation and at six months. At follow-up, while left ventricular ejection fraction was unchanged, mean cardiac output decreased by 15.6% (9.6 ± 2.9 L/min vs. 8.1 ± 2.3 L/min, p = 0.004) and left ventricular mass had regressed by 10% (166 ± 56 g vs. 149 ± 51 g, p = 0.0001). Significant improvements were also noted in right ventricular and biatrial structure and function. Aortic distensibility was unchanged at follow-up, but endothelial dependent vasodilatation had improved (2.5 ± 6.5% vs. 8.0 ± 5.9%, p = 0.04). Elective AVF ligation following successful renal transplantation is associated with improvements in left ventricular mass, right ventricular, and biatrial structure and function. Further randomized studies are warranted to determine the potential clinical improvement following AVF ligation in this cohort.

A study of the 16-Segment Regional Wall Motion Scoring Index and biplane Simpson's rule for the calculation of left ventricular ejection fraction: a comparison with cardiac magnetic resonance imaging.

AIMS: Accurate calculation of left ventricular ejection fraction (LVEF) is important for diagnostic, prognostic and therapeutic reasons. Cardiac magnetic resonance (CMR) is the reference standard for LVEF calculation, followed by real time three-dimensional echocardiography (RT3DE). Limited availability of CMR and RT3DE leaves Simpson's rule as the two-dimensional echocardiography (2DE) standard by which LVEF is calculated. We investigated the accuracy of the 16-Segment Regional Wall Motion Score Index (RWMSI) as an alternative method for calculating LVEF by 2DE and compared this to Simpson's rule and CMR. METHODS AND RESULTS: The 2D echocardiograms of 110 patients were studied (LVEF range: 7-74%); 57 of these underwent CMR. A RWMS was applied, based on the consensus opinion of two experienced cardiologists, to each of 16 American Heart Association myocardial segments (RWMSI: hyperkinesis = 3; normal regional contraction = 2; mild hypokinesis = 1.25; severe hypokinesis = 0.75; akinesis = 0; dyskinesis =-1). LVEF was calculated by: LVEF(%) =Σ(16segRWMS)/16×30. LVEF was calculated by Simpson's rule and CMR using standard methods. Results were correlated against CMR. Intertechnique agreement was examined. A P value of<0.05 was considered significant. RWMSI-LVEF correlated strongly with Biplane Simpson's rule (P< 0.001, r = 0.915). RWMSI-LVEF had a strong correlation to CMR (P < 0.001, r = 0.916); Simpson's rule-LVEF had a moderate correlation to CMR (P< 0.001, r = 0.647). In patients with LV dysfunction (EF < 55%), on linear regression analysis, RWMSI-LVEF had a better correlation with CMR than Simpson's rule. Further more Simpson's rule overestimated LVEF compared to CMR (mean difference: -6.12 ± 16.44, P = 0.002) whereas RWMSI did not (mean difference: 2.58 ± 14.80, P = NS). CONCLUSION: RWMSI-LVEF correlates strongly with CMR with good intertechnique agreement. In centers where CMR and RT3DE are not readily available, the use by experienced individuals, of the RWMSI for calculating LVEF may be a more simple, accurate, and reliable alternative to Simpson's rule.

Validation of cardiovascular magnetic resonance assessment of pericardial adipose tissue volume.

BACKGROUND: Pericardial adipose tissue (PAT) has been shown to be an independent predictor of coronary artery disease. To date its assessment has been restricted to the use of surrogate echocardiographic indices such as measurement of epicardial fat thickness over the right ventricular free wall, which have limitations. Cardiovascular magnetic resonance (CMR) offers the potential to non-invasively assess total PAT, however like other imaging modalities, CMR has not yet been validated for this purpose. Thus, we sought to describe a novel technique for assessing total PAT with validation in an ovine model. METHODS: 11 merino sheep were studied. A standard clinical series of ventricular short axis CMR images (1.5T Siemens Sonata) were obtained during mechanical ventilation breath-holds. Beginning at the mitral annulus, consecutive end-diastolic ventricular images were used to determine the area and volume of epicardial, paracardial and pericardial adipose tissue. In addition adipose thickness was measured at the right ventricular free wall. Following euthanasia, the paracardial adipose tissue was removed from the ventricle and weighed to allow comparison with corresponding CMR measurements. RESULTS: There was a strong correlation between CMR-derived paracardial adipose tissue volume and ex vivo paracardial mass (R2 = 0.89, p < 0.001). In contrast, CMR measurements of corresponding RV free wall paracardial adipose thickness did not correlate with ex vivo paracardial mass (R2 = 0.003, p = 0.878). CONCLUSION: In this ovine model, CMR-derived paracardial adipose tissue volume, but not the corresponding and conventional measure of paracardial adipose thickness over the RV free wall, accurately reflected paracardial adipose tissue mass. This study validates for the first time, the use of clinically utilised CMR sequences for the accurate and reproducible assessment of pericardial adiposity. Furthermore this non-invasive modality does not use ionising radiation and therefore is ideally suited for future studies of PAT and its role in cardiovascular risk prediction and disease in clinical practice.

Increasing identification of isolated left ventricular non-compaction with cardiovascular magnetic resonance: a mini case series highlighting variable clinical presentation.

BACKGROUND: Isolated left ventricular non-compaction (IVNC) was a previously rarely diagnosed condition with an apparent very poor prognosis. However, with high quality cardiac imaging with cardiac magnetic resonance (CMR) becoming increasingly available, it is being increasingly identified. However, asymptomatic patients with a serendipitous diagnosis of IVNC are being discovered, and their prognosis is less clear. We present our consecutive case series of four patients with this condition, and discuss the implications of their clinical presentation in context of the current literature. METHODS: Four patients in whom a CMR diagnosis of IVNC was established are presented. All CMR studies were performed on a Siemens Sonata 1.5T MRI scanner and phased array surface coil. ECG gated trueFISP (fast image with steady state precision) images were performed and analysed off-line with proprietary software. Where transthoracic echocardiography (TTE) had been performed it was retrospectively re-assessed for the diagnosis. RESULTS: In none of the four patients was a diagnosis of IVNC confirmed or even suspected until the CMR study. Two of the four patients were asymptomatic and identified serendipitously; aged 21 and 72 years, respectively. The other two presented for the investigation of ventricular dysrhythmias, and one of these had had a previous (incorrect) diagnosis of hypertrophic non-obstructive cardiomyopathy. CONCLUSIONS: Isolated left ventricular non-compaction is becoming increasingly identified and the initial poor prognosis described may not represent the true natural history of this condition. The long-term outlook for this asymptomatic cohort of patients with IVNC is unknown, but it may not be as sinister as first thought.