Absence of epicardial coronary stenosis in patients with systemic sclerosis with severe impairment of coronary flow reserve
Posted Nov 10 2010 6:14pm
Systemic sclerosis (SSc) is known to be characterised by a diffuse microvascular pathological process leading to cutaneous and visceral changes and to related clinical manifestations.
Both necropsy studies and in vivo investigations have shown that in a number of patients with SSc there is evidence of a coronary microvascular disease, while coronary artery disease does not exceed that seen in a control group. In particular, myocardial perfusion defects on thallium‐201 scintigraphy usually occur in the absence of angiographic evidence of coronary stenosis.
Recently, we used a new and non‐invasive method of contrast enhanced, transthoracic, second harmonic echo Doppler in patients with SSc to evaluate the coronary flow reserve (CFR), a functional variable measuring the ability of the coronary microvasculature to adapt its lumen to a vasodilating stimulus.
We detected a significant reduction of the CFR in 14/27 patients with SSc. In that study we did not examine the extramural tract of the coronary arteries; therefore, we could not exclude formally the possibility of a coronary stenosis which might have impaired the CFR.
To verify this possibility we assessed the status of the epicardial coronary arteries by a direct imaging test—the coronary contrast angiography with myocardial multidetector computed tomography (MDCT) —in seven of the patients with SSc previously found to have a markedly reduced CFR.
As previously reported, all these patients were asymptomatic for cardiac ischaemic manifestations. Table 1 gives the demographic and clinical data of these seven patients.
The myocardial MDCT examination was carried out by a multidetector computerised tomograph with eight lines of detectors and rotation time of 500 ms on 360° and with a slice depth of 1.3 mm (Light Speed Ultra, General Electric Medical Systems, Milwaulkee, Illinois, USA); retrospective gating was used. Non‐ionic contrast medium (120 ml) was injected at the speed of 4 ml/s, and the images were processed as appropriate on a SUN‐80 ULTRA workstation. The entire examination took 20–30 minutes. Image evaluation was carried out by an expert radiologist who knew the diagnosis of the patients. Figures 1A‐D show the images obtained in this study.
No defect in the coronary size and lumen was detected in any of the patient in this series. Parietal spots of calcium deposition were detected ( fig 1D1D )) only in one female patient (patient 4, aged 60 years) with high cholesterol serum levels (7.40 mmol/l; normal 2.60–5.20). The abnormal CFR value determined in this patient (CFR value 2.26) was within the range (2.37–1.78) of that of the other six patients tested.
This patient was not affected by cutaneous calcinosis.
The results of this study enable us to exclude the presence of coronary stenosis in our patients with SSc with severe CFR impairment. This investigation therefore demonstrates that the CFR impairment in these patients is not due to a primary stenosis of an epicardial coronary artery but to a primary dysfunction of the coronary microvasculature, as previously reported.
The non‐invasive MDCT test was preferred to conventional coronary angiography as it avoided cardiac catheterisation. Furthermore, the myocardial MDCT technique enabled the evaluation carried out by contrast echocardiography to be extended to all three coronary arteries. Moreover, this radiological diagnostic procedure is less expensive than conventional coronary angiography with catheterisation.
We believe that the two non‐invasive techniques employed may be complementary and combined in a sequential manner: CFR should be investigated first, then the MDCT scanning can be applied to patients with CFR pathological values.
In conclusion, this study demonstrates that the reduced CFR seen in this series of asymptomatic patients with SSc is not secondary to stenotic lesions of the major epicardial coronary arteries.