CMR Can Accurately Diagnose Cause of Heart Failure

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When patients present with heart failure of unknown origin, cardiovascular magnetic resonance (CMR) imaging is a safe and accurate alternative to coronary angiography for determining whether coronary artery disease plays a causative role. It may even be more affordable, according to a study published online September 6, 2011, ahead of print in Circulation.

To explore the best way to diagnose heart failure, Ravi G. Assomull, MRCP, of Royal Brompton Hospital (London, United Kingdom), and colleagues enrolled 120 consecutive patients who had experienced heart failure within the past 6 months. Exclusion criteria included prior CAD, chest pain, and significant valvular disease. Patients underwent both late gadolinium-enhanced CMR scanning and angiography. CMR was performed at a median interval of 43 days (range, 4-115 days) after index presentation, and the test preceded angiography in 68% of the cohort.

‘Gold-Standard’ Panel Makes the Call

CMR scans and angiograms were evaluated by separate 3-person teams of expert cardiologists. Another group of 3 cardiologists—referred to as the gold standard—reviewed all clinical, CMR, and angiographic data. In all 3 consensus groups, decisions were unanimous in the majority of cases.

According to the gold-standard group, 91 of the 120 cases (76%) had an underlying nonischemic etiology and thus were classified as dilated cardiomyopathy, while the remaining 29 cases (24%) had heart failure secondary to CAD. Using CMR as a gatekeeper would have hypothetically allowed 73% of the study cohort to avoid angiography.

The test showed diagnostic accuracy comparable to that of angiography (table 1).

Table 1. Diagnostic Accuracy of Angiography and CMR vs. Gold Standard

 

Sensitivity

Specificity

PPV

NPV

Diagnostic Accuracy

CMR

100%

96%

88%

100%

97%

Angiography

93%

96%

87%

98%

95%

Abbreviations: PPV, positive predictive value; NPV, negative predictive value.

All patients originally diagnosed with ‘true’ dilated cardiomyopathy (69%) or CAD (23%) retained the same diagnoses after 44.3 ± 11.5 months of clinical follow-up. In addition, Dr. Assomull and colleagues calculated the economic impact of the 2 imaging modalities. The cost per correct diagnosis was approximately $1,537 for CMR and $2,085 for angiography. Overall, using CMR as the gatekeeper to angiography would reduce the net cost per patient by about $1,495 (P = 0.001).

Late gadolinium-enhanced CMR “appears to be highly effective in detecting the basis of cardiac dysfunction in patients with newly diagnosed [heart failure] in whom the etiology is unclear. It is clinically effective and economically viable as a gatekeeper to [coronary angiography],” they conclude, stressing that potential cost savings depend on reimbursement rates and would vary in different health care systems.

In an e-mail communication, Dr. Assomull told TCTMD that for CMR to be dollar neutral, the test would need to cost at least 27.5% less than coronary angiography. “As CMR availability and expertise increases, the price of this relatively new investigation will undoubtedly continue to drop,” he added.

A First-Pass Alternative to Angiography

Current American College of Cardiology/American Heart Association guidelines recommend that heart failure patients be evaluated thorough detailed patient history, physical examination, laboratory investigations, and electrocardiography to ascertain the underlying cause and severity of disease, the paper reports. Angiography is recommended in any patients presenting with chest pain or significant ischemia, unless revascularization is not an option.

Dr. Assomull reported that angiography is still routinely performed in heart failure patients with no clinical evidence of underlying ischemia. “This traditional practice exposes the patient to a potentially unnecessary hazardous invasive investigation coupled with a significant dose of ionizing radiation,” he said. “Additionally, results from coronary angiography may confuse the clinical situation when potential ‘bystander’ single vessel disease is found and the underlying etiology of heart failure is not clear.”

CMR, on the other hand, is the “ideal investigation for this cohort of patients as it offers the ability to visualize scar consistent with previous myocardial infarction,” he said, noting that the absence of subendocardial scar coupled with MR-based imaging of the proximal coronary artery tree spared nearly three-quarters of the study cohort from angiography. “Unlike coronary angiography, CMR also provides the potential for further risk stratification of these patients by identifying the presence of midwall scar that is now widely recognized as a predictor of poor outcome in patients with non-ischemic heart failure.”

Study Details

CMR was performed using the Magnetom Sonata 1.5T (n = 42) or Magnetom Avanto (n = 78), both manufactured by Siemens (Malvern, PA). Data were analyzed using CMRtools semiautomated software (Cardiovascular Imaging Solutions, London, United Kingdom).

For the economic analysis, the cost per angiogram was obtained from the 2008 to 2009 UK National Health Service tariffs, while the cost per CMR represented current prices within the health care system.


Source:
Assomull RG, Shakespeare C, Kalra PR, et al. Role of cardiovascular magnetic resonance as a gatekeeper to invasive coronary angiography in patients presenting with heart failure of unknown etiology. Circulation. 2011;124:1351-1360.

 

 

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Disclosures
  • The study was supported by the National Institute for Health Research Cardiovascular Biomedical Research Unit at Royal Brompton Hospital and Harefield NHS Foundation Trust and Imperial College London.
  • Dr. Prasad reports no relevant conflicts of interest.

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