Indian Journal of Nuclear Medicine

CASE REPORT
Year
: 2017  |  Volume : 32  |  Issue : 4  |  Page : 348--350

Single coronary artery demonstrating slightly decreased 13NH3Stress flows in its distal flow territories


Sabrine Q Kol1, Jouke J Boer2, Friso M van der Zant3, Remco J J. Knol3,  
1 Department of Medical Imaging (Nuclear Medicine and Radiology), Northwest Clinics, Alkmaar; Department of Medical Imaging (Nuclear Medicine and Radiology), VU University Medical Center, Amsterdam, The Netherlands
2 Department of Medical Imaging (Nuclear Medicine and Radiology), Northwest Clinics, Alkmaar; Department of Radiology and Nuclear Medicine, Meander Medical Centre, Amersfoort, The Netherlands
3 Department of Medical Imaging (Nuclear Medicine and Radiology), Northwest Clinics, Alkmaar; Cardiac Imaging Division Alkmaar, Northwest Clinics, Alkmaar, The Netherlands

Correspondence Address:
Sabrine Q Kol
Department of Medical Imaging (Nuclear Medicine and Radiology), VU University Medical Center, De Boelelaan 1117, 1081HV, Amsterdam
The Netherlands

Abstract

A 54-year-old male patient was referred for computed tomography angiography to rule out cardiovascular disease. The examination revealed a single coronary artery originating from the right sinus of Valsalva, extending to the normal left circumflex artery and left anterior descending artery domains. The computed tomography showed only mild coronary sclerosis. The myocardial stress flow on the subsequently performed 13NH3myocardial perfusion positron emission tomography demonstrated a relative stress flow reduction in the distal segments along the monocoronary. In the presented patient without significant coronary disease and a benign course of the monocoronary, the relative inability to increase blood flow during stress in the distal segments of the artery is a remarkable finding.



How to cite this article:
Kol SQ, Boer JJ, van der Zant FM, J. Knol RJ. Single coronary artery demonstrating slightly decreased 13NH3Stress flows in its distal flow territories.Indian J Nucl Med 2017;32:348-350


How to cite this URL:
Kol SQ, Boer JJ, van der Zant FM, J. Knol RJ. Single coronary artery demonstrating slightly decreased 13NH3Stress flows in its distal flow territories. Indian J Nucl Med [serial online] 2017 [cited 2021 Sep 17 ];32:348-350
Available from: https://www.ijnm.in/text.asp?2017/32/4/348/216550


Full Text



 Introduction



A single coronary artery (SCA) is an uncommon coronary anomaly that may go unnoticed, but could result in major cardiac complications when the artery has a malignant course. Little is known about myocardial perfusion in patients without or with only minor coronary plaques of such SCA. The present case demonstrates a patient with a single coronary artery showing a benign coarse and without significant plaques, yet with slightly decreased 13NH3 stress flows in its distal territories.

 Case Report



A 54-year-old Caucasian male patient presented with angina-like chest pain to the cardiology outpatient clinic of our hospital. His cardiovascular risk profile included smoking, hypercholesterolemia, a body mass index of 29 kg/cm 2, and a family history of cardiovascular disease. The patient had no other relevant medical history and did not use any medication at presentation. Results of his physical examination, electrocardiogram, echocardiogram, and cycle ergometer test were normal. On coronary computed tomography angiography (CCTA), a single coronary artery (SCA) with benign course originating from the right sinus of Valsalva was visualized [Figure 1], left panel], whereas no left main coronary artery was originating from the left sinus of Valsalva [Figure 1], right panel]. The path of the SCA ran along the usual domain of the left circumflex artery (LCX) and subsequently along the left anterior descending artery (LAD) domain providing all regular side branches [Figure 2]a. At calcium scoring, an Agatston score of 59.9 was calculated consistent with only a mild grade of coronary artery disease. The CCTA revealed two calcified plaques with minimal stenosis in both the proximal SCA (corresponding with the right coronary artery [RCA] domain) and the mid part of the vessel corresponding with the LCX domain. The successively performed coronary angiography (CAG) [Figure 2]b confirmed the presence of only minimal luminal stenosis. The patient received medication to treat his hypercholesterolemia, comprising simvastatin. Due to concerns expressed by the patient, 35 months later, a 13 NH3 myocardial perfusion positron emission tomography (PET) was performed with low-dose CT attenuation correction with and without adenosine stress (0.14 mg/kg/min during 6 min) to further rule out flow limitations. Myocardial perfusion was evaluated by means of the Syngo MBF software package (Siemens Healthcare, Knoxville, Tennessee, USA) using the conventional three-vessel model [territories superimposed on the polar plots in [Figure 3], which was feasible for this purpose in the present case since all regular side branches are present and appeared to be positioned normally. The 13 NH3 myocardial perfusion PET/CT demonstrated homogeneous tracer uptake throughout the myocardium of the left ventricle [Figure 3], with normal stress and rest left ventricular ejection fractions. Remarkably, the regional myocardial stress blood flow [Table 1] demonstrated a relative perfusion reduction of 26% and 23%, respectively, in the typical LAD and LCX flow territories compared to myocardial stress blood flow in the RCA territory. Follow-up during 20 months revealed no new findings, major cardiac events, or resubmission to the outpatient clinical heart unit.{Figure 1}{Figure 2}{Figure 3}{Table 1}

 Discussion



SCA refers to the origin of both the RCA and the left coronary artery from a single ostium originating from the aortic trunk, supplying the entire heart. This anomaly is rare with a reported prevalence of 0.014%–0.066%.[1],[2] Different types of anomalies of the SCA have been described in literature such as a single coronary arising from the left cusp and dividing into the RCA and LD with the RCA traveling posterior to the aorta, or the LCX can arise from the right aortic cusp and then progress posterior to the aorta, or the RCA can arise from the root of the aorta.[3] Generally, this variant goes unnoticed and is usually encountered during CCTA, CAG, or at autopsy. A higher incidence has been recorded in association with other types of congenital heart anomalies, for example, in patients with tetralogy of Fallot, an SCA was found in 2.4% of the patients.[1]

The prognostic significance is dependent on the course of the SCA. This translates to the majority of patients with a benign course usually being asymptomatic and patients with a malignant course being at risk of sudden death. Maron et al. reported a malignant course to be the second most common cause of sudden death in young athletes following hypertrophic cardiomyopathy.[4]

Some subgroups of SCA are more likely to lead to angina pectoris, ischemia, or even acute myocardial infarction. Fifteen percent of the patients with an SCA may have myocardial ischemia due to a malignant anatomy without atherosclerotic disease.[5] Factors such as the presence of a slit-like ostium, an ostial ridge, and an acute-angle takeoff course of the coronary artery can contribute to the possible presence of ischemia. The course of the SCA in our patient was benign and did not have a slit-like ostium or acute-angle take off.

Previous investigations of myocardial perfusion have demonstrated the ability of PET imaging to reveal coronary endothelial and microcirculatory dysfunction occurring in patients with coronary risk factors such as hypercholesterolemia, smoking, diabetes mellitus, and essential hypertension.[6] The patient was diagnosed with hypercholesterolemia at the time of presentation and was also a smoker. The Agatston score showed only a mild grade of coronary artery disease, which was confirmed by both the CCTA and CAG, showing no significant stenosis. The 13 NH3-PET revealed relative and gradual stress blood flow reduction in the distal flow territories along the SCA, which was not perceived in the proximal territory. Quantitative analysis is more accurate in detecting such subtle perfusion differences, especially when overall perfusion is within normal limits. By visual appraisal only, this can easily be overlooked. If, in our patient, coronary endothelial damage and microcirculatory dysfunction were present due to hyperlipidemia or history of smoking, it is expected to result in more diffuse perfusion reduction in all territories and not merely in the distal segments.

The coronary vasculature has an auto-regulation system that allows it to maintain basal resting flow over a range of pressures along the coronary tract. The coronary blood flow is then determined by the pressure gradient across the myocardial vasculature and vascular resistance.[7] During pharmacological stress, this pressure gradient changes due to vasodilation, resulting in a change of myocardial blood flow. One possible explanation for the perfusion pattern in the present case may be a relatively more pronounced drop in pressure and vascular resistance during vasodilation in the proximal part as compared to the distal part of the SCA as compared to a situation with normal coronary anatomy. This decrease in pressure gradient over the full length of this vessel could result in a relative inability to increase flow in distal segments in the same degree as the proximal segments. The relative difference in myocardial stress flow as demonstrated in this patient could be more pronounced due to the presence of risk factors.

Unfortunately, there are insufficient data about flow characteristics in SCAs. Expectantly, with the increase in diagnostic cardiovascular imaging, more coronary anomalies will be encountered resulting in more data on this rare coronary anomaly.

To the best of our knowledge, this is the first case of PET-CT cardiac perfusion imaging evaluation in a patient with a benign SCA in which reduced flow in the distal path of the monocoronary is documented, in the absence of significant coronary disease.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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