Evaluation of a shortened cardiac MRI protocol for left ventricular examinations: diagnostic performance of T1-mapping and myocardial function analysis

Abstract

Background: In this study we sought to retrospectively evaluate whether a very brief cardiac magnetic resonance imaging (CMR) protocol sufficiently distinguishes patients with relevant myocardial changes with need for further examination from healthy subjects.

Methods: Patients with clinical indication for CMR (n = 160) were included in the study. Patients were categorized into two groups depending on presence of left ventricular (LV) dysfunction. ROC-analysis was done for results of T1-, T2- mapping and extracellular volume evaluation in patients without LV dysfunction. Binary endpoint was correctly depicted pathology of the conventional qualitative CMR techniques and report.

Results: In the patient cohort without LV dysfunction (49%), AUC for T1 mapping was 82% (p < 0.001), 60% for T2 mapping (p = 0.1) and 79% for ECV (p < 0.001). T1 mapping was significantly superior to T2 mapping to rule out left ventricular pathology (p = 0.012). Sensitivity for the combined use of T1 mapping and sBTFE cine imaging was 98%; the negative predictive value was 90%. In 49 patients (30%) full protocol CMR did not provide any additional information; T1 mapping correctly detected 57% of the subjects from this group who would not benefit from additional CMR.

Conclusion: A shortened CMR protocol comprising T1 mapping and LV-function analysis seems suitable to rule out myocardial alterations. Every third patient of the study population did not benefit from full contrast enhanced CMR. The shortened protocol correctly identified every fifth patient who would not benefit but no relevant pathologic findings with the obligation for treatment were missed.

Keywords: CMR; Cardiac MRI; Economic; Shortened protocol; T1mapping.

Fig. 1

Example of an 18-year-old male patient with severe myocarditis. Native sequences: T2w dark blood (top row) and native T1 mapping in short axis (middle row) and 4 chamber view (lower row) at acute state,8 and 16 weeks follow up exam (columns from left to right). Highest T1 relaxation time in this patient was 4 standard deviations above values of volunteers and well above our threshold in acute state and within normal range at follow-up. It is of note that T2w imaging appears to be normal due to inflammatory involvement of the whole heart. Even the ratio of myocardium and skeleton muscle signal intensity was normal as a result of accompanying myositis

Fig. 2

Example of an 18-year-old male patient with severe myocarditis. Contrast enhanced sequences: CE T1 mapping in short axis and 4 chamber view (first two rows) and Late-Gadolinium-Enhancement (last two rows) at acute state and 8 and 16 weeks follow up exam (columns from left to right). Maximum ECV was 51% in acute state in the anterior septal wall and 25% at 16 week follow up

Fig. 3

shows a ROC analysis of the three quantitative techniques (T1 mapping [solid line], T2 mapping [dotted line] and extracellular volume [dashed line]) in patients with no left ventricular dysfunction where additional T2 mapping was available (n = 56)

Fig. 4

shows the flow chart of diagnostic outcomes in our study population based in presence of LV dysfunction and T1 relaxation times. All patients received full contrast CMR. It further illustrates the groups that benefit form full contrast enhanced CMR and also those who do not. The discrimination of this groups is also shown for a threshold value of T1 mapping (1300 ms)