Cardiovascular Magnetic Resonance for Visualization of Myocardial Ischemia at Rest

Sigita Glaveckaitė1, 2, Darius Palionis1, 3, Nomeda Rima Valevičienė1, 3, Valdas Bilkis1, 2, Jūratė Aganauskienė-Burkuvienė1, 2, Pranas Šerpytis1, 2, Aleksandras Laucevičius1, 2 1Clinic of Heart and Vascular Medicine, Faculty of Medicine, Vilnius University, 2Centre of Cardiology and Angiology, Vilnius University Hospital Santariškių Klinikos, 3Centre of Radiology, Vilnius University Hospital Santariškių Klinikos, Lithuania


Introduction
We present a case of resting myocardial ischemia and shortly discuss the value of cardiovascular magnetic resonance (CMR) for the assessment of rest and stress ischemia especially in case when coronary artery stenosis is of unclear signifi cance.

Case Report
A 54-year-old male was admitted to the Vilnius University Hospital Santariškių Klinikos because of typical angina pectoris during minimal physical activity and at night.
From the age of 48 years, the patient suffered from arterial hypertension and angiospastic angina pectoris with normal coronary arteries on conventional angiography (COG) and normal left ventricular (LV) function on echocardiographic examination.Treatment with calcium channel blockers was effective.At the age of 54 years, the patient experienced renewed angina pectoris during physical activity.He was treated in our hospital; COG showed minimal changes: 50% stenosis in the fi rst diagonal branch of the left anterior descending artery (LAD).Treatment with calcium channel blockers was continued.Echocardiogram and electrocardiogram (ECG) were without signifi cant pathological changes.
In two weeks after the abovementioned hospitalization, the patient was repeatedly admitted to our hospital because of exacerbation of angina pectoris with a frequent need for nitrates.Initial ECG revealed a sinus rhythm (80 bpm) with the electrocardiographical features of left ventricular hypertrophy.Serial troponin I tests showed negative results.The repeated echocardiogram showed diminished LV ejection frac-tion of about 45% and mild hypokinesis in the anteroseptal wall.Because of previous equivocal fi ndings on COG in order to confi rm inducible ischemia, stress CMR (1.5 T Siemens Avanto) was scheduled.Rest short-axis cine MR imagining showed akinesis in the anteroseptal and anterior walls at the midventricular level and hypokinesis in the anterior and lateral walls at the apical level (Fig. 1).A rest perfusion MR scan revealed a nearly transmural perfusion defect in the midventricular segments of the anterior and anteroseptal walls and in the apical segment of the anterior wall (Fig. 2A).On late gadolinium enhancement (LGE) images 15 minutes after contrast medium injection, no contrast enhancement in the LV was noted (Fig. 2B).Findings on CMR scan showed ischemia in theoretical LAD territory at rest; therefore, a stress test was postponed.COG was performed, and this time, a signifi cant stenosis of about 85% was noted in the fi rst diagonal branch of the LAD (Fig. 3).The patient underwent successful primary stenting of the fi rst diagonal branch of the LAD.

Discussion
The management of patients with chest pain is a common and challenging clinical problem.Multiple imaging strategies have been used to accelerate the diagnosis and to provide further risk stratifi cation in patients with no initial evidence of acute coronary syndrome.
In our case, not only various noninvasive tests such as bicycle exercise testing, bicycle exercise echocardiography, dobutamine stress echocardiography, single-photon emission computed tomography, vasodilator perfusion CMR, or dobutamine  stress function CMR, but also myocardial fractional fl ow reserve measured invasively could be used in order to assess inducible ischemia and to validate the need for revascularization.According to our expertise, CMR was chosen because of its capability for combined assessment of function, perfusion, and LGE, safety for the patient, high sensitivity and specifi city for detecting a relevant coronary stenosis in patients with suspected coronary artery disease and its ability to exclude another pathology (e.g., myocarditis, aortic disease, etc.).A noninvasive stress test before invasive procedure was chosen because of previous equivocal fi ndings on COG.
The combination of CMR function, stress perfusion, and LGE allows for the use of CMR as a primary form of testing for the following: 1) identifying the patients with ischemic heart disease when resting ECG abnormalities or inability to exercise are present; 2) defi ning the patients with large-vessel coronary artery disease and its importance for candidates for interventional procedures; or 3) determining the patients who are appropriate candidates for interventional procedures (1).According to the appropriateness criteria for CCT/CMR (2), vasodilator perfusion CMR or dobutamine stress function CMR is a generally acceptable and reasonable ap- proach for the assessment of coronary stenosis, the signifi cance of which is unclear after coronary angiography (catheterization or computed tomography).The combination of CMR perfusion and LGE assessment for detecting a relevant coronary stenosis in patients with suspected coronary artery disease yielded a sensitivity and a specifi city of 0.94 and 0.87; in PCI patients, 0.91 and 0.90; and in CABG patients, 0.79 and 0.77, respectively (3).
In our case, CMR was capable of proving rest ischemia in theoretical LAD territory, excluding a myocardial scar, and validating the need for revascularization.

Statement of Conflict of Interest
The authors state no confl ict of interest.

Fig. 1 .
Fig. 1.Short-axis cine magnetic resonance images (SSFP sequence) at rest at the midventricular level in end-diastole (A) and end-systole (B) Akinesis in the anteroseptal and anterior segments was observed (please note the absence of the thickening of anterior and anteroseptal segments in end-systole [arrows]).

Fig. 2 .
Fig. 2. The rest perfusion magnetic resonance image (A) shows a nearly transmural hypointense perfusion defect in the anterior wall at the midventricular level (arrows), and on late enhancement image 15 minutes after contrast media injection (inversion recovery sequence) (B), no late gadolinium contrast hyperenhancement was noted at the corresponding slice as in (A)

Fig. 3 .
Fig. 3. Coronary angiograms showing signifi cant stenosis in the fi rst diagonal branch of the left anterior descending artery (arrow, A) and good angiographic results after primary stenting of the fi rst diagonal branch of the left anterior descending artery (arrow, B)