Acute coronary syndrome caused by compression of the left main coronary artery – the usefulness of computed tomography in diagnosis and interventional treatment planning

Case report

A 46-year-old female patient with severe idiopathic pulmonary hypertension treated with sildenafil and a prostacyclin analogue in NYHA class III/IV was transferred to the Institute of Cardiology because of anginal pains. Crescendo angina had begun a few weeks before the hospitalization and in the recent period had taken the form of recurrent resting pains. Electrocardiogram showed right bundle branch block with oscillating myocardial ischaemia during angina.

Echocardiographic examination confirmed the presence of pulmonary hypertension with aneurysmal dilation of the pulmonary trunk (maximal diameter of 44 mm) and a dilated, hypokinetic right ventricle. Left ventricular contractility and volume were assessed as normal. Laboratory examinations demonstrated an increased troponin level. Because of the patient’s clinical instability an emergency computed tomography (CT) of the coronary arteries was performed.



Diagnostic imaging and treatment planning



The study was performed using a 128 slice dual source scanner (Somatom Definition Flash – Siemens, Germany) and an acquisition protocol optimized for the assessment of coronary arteries. Because of the fast resting heart rate (82 bpm) a protocol with retrospective ECG gating was used. Scan time was 4.8 s and 60 ml of a high-iodine concentration contrast agent (Iomeron 400 – Bracco, Italy) was administered. Total radiation dose of the study was 6.2 mSv.

Computed tomography excluded the presence of coronary anomalies and atherosclerotic plaques in coronary arteries, but showed a critical stenosis of the ostium of the left main coronary artery (LMCA) caused by compression from the aneurysmally dilated pulmonary trunk (Figure 1 A-F). Minimal lumen area of the left main coronary artery was less than 3.0 mm².

Because of the unstable clinical condition, after detailed assessment of the anatomical relations shown in computed tomography, the patient was offered treatment by means of a percutaneous coronary intervention.

Computed tomograhy allowed a precise assessment of the anatomical conditions and therefore permitted planning of the percutaneous coronary intervention. MPR, cMPR and VRT reconstruction images were used to assess the length of the LMCA, the length of stenosis and the reference diameter of the vessel (Figure 2 A-D). Precise assessment of the lesion length was also possible by means of transverse views similar to those obtained with intravascular ultrasound (Figure 2 A-D). Image analysis permitted planning of the procedure consisting of stent implantation to the proximal LMCA segment without the need of bifurcation involvement.

After signing informed written consent the patient received dual antiplatelet therapy and was prepared for the procedure.



Percutaneous coronary intervention



Left main coronary artery stenosis was not seen in the few initial, typical left coronary artery views (Figure 3 A-C). Additional, atypical views planned according to the CT scan were necessary to demonstrate the compression of the left main ostium (Figure 4 A-B). It was impossible to find a view showing the ostium and the bifurcation of the left main coronary artery at the same time. Therefore precise planning of the stent length based solely on coronary angiography might have been inaccurate. Finally, based on the CT measurements, a stent of 4.0 mm diameter and 12 mm length was chosen (Figure 4 C). Optimal stent length was confirmed in two views (Figures 4 C, 5 A). The stent was post-dilated with a short (10 mm) high-pressure (non-compliant) balloon to reach the reference diameter of the vessel assessed by CT (Figure 5 B). A very good angiographic effect of the procedure was obtained (Figure 5 C).

No complications of the procedure were observed. There were no anginal pains in the days following the procedure. Slow normalization of the myocardial necrotic markers was noted.

Discussion

The described case emphasizes the key role of non-invasive imaging by means of computed tomography in reaching a diagnosis and treatment planning in a patient with atypical pathology. It is probably the first in Poland and one of the few described cases where CT allowed a fast, safe and accurate diagnosis of an external compression of the left main coronary artery by a markedly dilated pulmonary trunk [1-3]. An indisputable advantage of CT is its possibility to assess anatomical structures beyond assessment of the coronary artery lumen. Data obtained during the CT scan are used for construction of two- or three-dimensional reconstructions which in the present case permitted us to form a definitive diagnosis and to plan an optimal method of treatment. In contrast to classic coronary angiography, CT scan does not have limitations which could in some cases exclude the possibility of a reliable assessment of the vessel length and its reference diameter.

The knowledge about the angiographic picture of the patient before her arrival in the catheterization laboratory permitted us to:

1) choose the optimal treatment method (in the present case cardiac surgery was denied due to high risk),

2) collect the informed consent in a comfortable way for the patient,

3) initiate pre-procedural pharmacotherapy, and

4) prepare for the percutaneous procedure (choose a guiding catheter or the right stent in terms of its diameter, length and maximal radial force).

Information based on the good quality images from computed tomography are useful in planning of the interventional and surgical revascularization, not only in the present case, but also in patients with atherosclerotic changes [4, 5]. Computed tomography data have similar quality to coronary angiography supplemented by intravascular ultrasound. In the present case, information about the results of the CT scan was known to the treating physician and to the interventional cardiologist and therefore permitted correct treatment planning and safe conduction of the procedure.

References

 1. Dodd JD, Maree A, Palacios I, et al. Left main coronary artery compression syndrome evaluation with 64-slice cardiac multidetector computed tomography. Circulation 2007; 115: e7-e8.

 2. Bonderman D, Fleischmann D, Prokop M, et al. Left main coronary artery compression by the pulmonary trunk in pulmonary hypertension. Circulation 2002; 105: 265.

 3. Safi M, Eslami V, Shabestari AA, et al. Extrinsic compression of left main coronary artery by the pulmonary trunk secondary to pulmonary hypertension documented using 64-slice multidetector computed tomography coronary angiography. Clin Cardiol 2009; 32: 426-428.

 4. Pregowski J, Kepka C, Kruk M, et al. Comparison of usefulness of percutaneous coronary intervention guided by angiography plus computed tomography versus angiography alone using intravascular ultrasound end points. Am J Cardiol 2011; 108: 1728-1734.

 5. Kepka C, Opolski MP, Juraszynski Z, et al. Computed tomography to predict surgical revascularization of a left anterior descending artery occlusion incompletely visualized by conventional angiography. J Thorac Imaging 2011 Jul 26. [Epub ahead of print] PubMed PMID: 21795996.