Asian Heart Institute, Mumbai, India
Clinical History
A 42-year-old female presented with shortness of breath on exertion (New York Heart Association (NYHA) class II) for 3 months. Her past history was significant for chronic hypertension following a hypertensive disorder of pregnancy for 7 years, long standing subclinical hypothyroidism and recently diagnosed bronchial asthma. Twelve lead electrocardiogram (ECG) done at a local hospital showed T wave inversion and non-specific ST segment changes in the high lateral leads (lead I and aVL) and q waves in aVL (Figure 1). Her cardiac enzymes were within normal limits. A 2-D transthoracic echocardiogram (TTE) revealed a mildly dilated left ventricle (LV), mildly reduced systolic function with a left ventricular ejection fraction (LVEF) of 40-45%, regional wall motion abnormality characterised by hypokinetic mid and apical anterior walls with grade I diastolic dysfunction.
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| Figure 1. 12 lead ECG showing sinus rhythm. Non-specific ST segment changes and T wave inversion in high lateral leads I and aVL, Q waves in aVL and mildly prolonged QT interval (QTc: 474ms). |
The patient was referred to our institute for further management. Catheter angiography revealed a discrete lesion causing approximately 80% narrowing in the proximal part of a medium calibre diagonal artery that was the only diagonal branch in this patient. Additionally, there was complete right coronary artery (RCA) ostial occlusion flush with the aortic interface rendering ostial cannulation exceedingly difficult. The entire dominant RCA filled retrogradely via robust collaterals from the left coronary system till the complete cut-off at right coronary ostium (Rentrops III collaterals) (Figure 2, Movie 1). Intracoronary nitrate was not administered during the procedure.
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| Figure 2. (a) Left anterior oblique (LAO) caudal (Spider view) catheter angiography image demonstrates high origin of a single diagonal artery of good calibre. A discrete short segment lesion in proximal diagonal artery causing severe (80-85%) luminal stenosis (white arrows). The left main coronary artery (LM), left anterior descending artery (LAD) and left circumflex artery (LCX) appear normal. (b) Aortic root angiogram depicts complete cut off at right coronary artery (RCA) ostium and absent antegrade contrast flow in RCA (black arrow). |
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| Movie 1. LAO caudal selective LM angiography unlabeled (A) and labeled (B) showing retrograde collateral filling of the RCA tree from the septal perforator branches of the LAD extending up to the RCA ostium (Rentrops III collaterals). |
CMR Findings
Since functional evaluation had direct implications for clinical management, the patient was referred for cardiovascular magnetic resonance (CMR) imaging on a 1.5 T Multiva (Philips Healthcare, Best, The Netherlands) to evaluate LV and right ventricular (RV) volumes and function, assess myocardial viability in the diagonal artery territory, and rule out inducible ischemia or micro-infarction in the collateral-dependent RCA distribution. Since the patient had recently diagnosed, mild, well-controlled bronchial asthma with clear breath sounds bilaterally, no active wheezing, no ongoing maintenance medications and no recent exacerbations; formal clearance for standard adenosine pharmacological stress was documented by her pulmonologist. Pre-procedural preparation included a 4-hour fast, confirmed 24-hour abstinence from dietary caffeine (coffee, tea, chocolate and colas) and verification that the patient was not taking methylxanthines (theophylline or aminophylline).
Baseline vitals documented a heart rate of 54 bpm, blood pressure of 118/76 mmHg and body weight 77 kg. Following entry into the scanner bore, continuous vectorcardiographic monitoring and automated blood pressure cycling every 60 seconds were initiated. Morphological and functional imaging commenced with a T1-weighted (T1w) black blood single shot turbo spin echo (TSE) axial stack, T2-weighted (T2w) Short-Tau Inversion Recovery (STIR) TSE axial stack and balanced turbo field echo (TFE) cine sequences in standard 2-chamber, 4-chamber, and short-axis views.
Continuous intravenous adenosine was then administered at 140 µg/kg/min (infusion rate: 10.78 mg/min; total dose: ~43 mg) over 4 minutes. The patient verbally confirmed transient facial flushing and chest warmth during the second minute. Peak hyperaemia was established at the third minute (heart rate increased to 78 bpm; blood pressure dropped to 106/68 mmHg). At 3 minutes and 15 seconds into the infusion, a 15.4 mL bolus of gadopentetate dimeglumine (concentration: 0.5 mmol/ml, contrast dose: 0.1 mmol/kg) was injected at 5.0 mL/s, followed immediately by a 25 mL saline flush at the same rate. Dynamic first-pass stress perfusion was acquired across 50 cardiac cycles using a multi-slice saturation-recovery balanced TFE sequence.
Following dynamic acquisition, the adenosine infusion was terminated with complete symptom resolution within 60 seconds. Early gadolinium enhancement (EGE) imaging was performed at 5 minutes using Inversion Recovery (IR) TFE sequence with fixed inversion time (TI) of 440 ms followed by late gadolinium enhancement (LGE) imaging at 10 minutes with incremental TI values (starting at 340 ms) based on an IR TFE scout. Quantitative and functional analysis revealed moderate LV systolic dysfunction (LVEF 32%), mildly dilated LV with a LV end-diastolic volume index (LVEDVI) of 100ml/m2 (normal range: 49-97 ml/m2), and reduced index LV stroke volume of 33ml/m2 (normal range 38-67 ml/m2). Indexed myocardial muscle mass was 69 gm/m2 (normal range 45-70 gm/m2). There was regional wall motion abnormality in the form of akinesia in mid to apical anterior and apical lateral segments with associated mild myocardial thinning (Movie 2). There was no myocardial edema on STIR images (Figure 3). Qualitative analysis of stress perfusion images confirmed uniform contrast wash-in and an absence of dark-rim or susceptibility artifacts in the inferior septum and inferior segments, ruling out inducible ischemia in the collateralised right coronary territories. Sub-endocardial perfusion defects were seen in mid to apical anterior and apical lateral segments (Figure 4). EGE images revealed no microvascular obstruction (MVO) or intracavitary thrombus. On LGE images a dense transmural infarction was seen in distal basal, mid, and apical anterior and apical lateral segments that matched with the stress perfusion defects in the diagonal territory. There was an infarct in the anterolateral papillary muscle limited to its superior half (Figure 5). The total scar burden was calculated at 25% of the total myocardial mass using a 5-standard deviation threshold above remote normal myocardium. The discrepancy between the CMR and TTE derived measurement of LVEF likely stemmed from TTE relying on geometric assumptions which often overestimate global systolic function when asymmetric regional akinesia is present.
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| Figure 3. Balanced cine TFE at end-diastole still frames (a-c). (a) Four chamber image shows mildly dilated LV. Short axis images at mid (b) and apical (c) cavity levels show mild thinning of mid anterior segment (arrow) and apical anterior segment (arrow). (d) STIR mid short axis image reveals no evidence of myocardial edema. |
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| Video 2. Balanced TFE short axis cine stack (A) demonstrating akinesia of mid and apical anterior and apical lateral segments with normal wall motion in rest of the RV and LV myocardium. Balanced TFE 2 chamber cine stack (B) demonstrating akinesia of mid and apical anterior walls. |
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| Figure 4. Multi-slice saturation-recovery balanced TFE CMR stress perfusion short axis stack images (a to d). (a) No perfusion defect seen in proximal basal LV myocardium. (b, c) Mid-cavity images reveal subendocardial perfusion defects in mid anterior segment (arrow). (d) Apical cavity image reveals a subendocardial perfusion defect in the apical anterior (red arrow) and apical lateral segments (white arrow). There was no visual evidence of stress induced sub-endocardial or transmural perfusion defects in the inferior or the inferoseptal segments corresponding to the RCA territory. |
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| Figure 5. IR TFE LGE short axis images (a to f) revealing transmural scar in distal basal anterior(a), mid anterior (b and c), apical anterior and apical lateral segments (d, e, f) of diagonal territory matching with the stress perfusion defects. Due to dual blood supply, infarct of the anterolateral papillary muscle was limited to its superior half, with sparing of the inferior half (yellow arrow in b). The extensive anterior wall transmural infarct was corroborated on delayed enhancement 2 chamber image (g). |
Conclusion
Coronary computed tomography angiography (CorCTA) was then performed for anatomical mapping of the RCA ostial occlusion and simultaneous assessment of the diagonal artery stenosis. Aortic root had normal dimensions measuring 3.4 x 3.2 x 3.3 cm in maximum cusp to commissure diameters. A focal saccular outpouching was seen arising from the right sinus of Valsalva measuring 3 x 12 x 9 mm directed towards right ventricular outflow tract (RVOT). The RCA exhibited an anterior (1 o’clock) and severely acute take off (take-off angle 17º) from this outpouching, with a partial low inter-arterial course between RVOT and the aortic root for a length of 6 mm. There was focal non contrast opacification of the RCA ostium (segment length <1 mm) There was mild mural thickening and focal calcification in the wall of RCA sinus (Movie 3). Although high-risk markers such as an acute-angled take-off, absent pericoronary fat, and reduced interluminal space distance in the ostioproximal segment suggested an anomalous course of the RCA, the presence of an intramural component could neither be confirmed nor excluded due to the compounding effects of extrinsic compression by the saccular bulge of the sinus of Valsalva at the RCA origin (Movie 3). Multi-phase reconstruction demonstrated that the RCA ostial lumen remained completely closed during both systole and diastole (Figure 6). No obvious large calibre collateral to the RCA could be visualised on CorCTA. Concurrently, a non-calcified, concentric luminal narrowing with hazy vessel margins, without associated calcification or discernible atherosclerotic plaque of length 7 mm and 80-85% diameter stenosis was seen in the proximal diagonal artery (Movie 3, Figure 7). No additional atherosclerotic plaques or significant luminal stenoses were identified within the rest of coronary arteries.
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| Figure 6. CorCTA (a) double oblique sagittal reformat images of the RCA ostium depicting the saccular outpouching from the right sinus of Valsalva (black arrows) protruding towards the RVOT (white asterisk) and RCA ostial occlusion (yellow arrow) with normal diameter and contrast opacification of the segment distal to the ostium. (b) Sagittal oblique image for the ascending aorta demonstrating the measurement of the saccular outpouching. (c) Axial oblique images at 75% (mid-diastolic) phase reconstruction and (d) at 45% (end systolic phase) reconstruction demonstrate complete RCA ostial occlusion (yellow arrows in c and d). (e) Three dimensional (3D) maximum intensity projection (MIP) reconstruction image depicting concurrent RCA ostial cut-off (yellow arrow) and stenosis in diagonal artery (black arrow). |
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| Movie 3. CorCTA double-oblique axial reformat images (A) of the aortic root demonstrating the anterior origin (1 o’clock) and severely acute angled take off of RCA with a partial low inter-arterial course between aortic root and RVOT, mural thickening and calcification in the right sinus of Valsalva wall and non-opacification of RCA ostium. Immediately distal to the ostial occlusion, RCA bifurcates into a well opacified main RCA trunk and a prominent conus branch, possibly filled retrogradely through bridging micro-collaterals. Concomitant focal stenosis visualised in proximal diagonal artery. CorCTA double oblique coronal reformat images (B) of the RCA ostium demonstrating the small saccular outpouching at the origin of RCA that protrudes towards RVOT with RCA ostial occlusion. |
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| Figure 7. CorCTA images of the diagonal artery (D1). (a) Straight and (b, c, d) curved multiplanar reformatting (MPR) images demonstrate a short segment (7 mm), non-calcified, tubular, severe luminal stenosis of approximately 80-85% with hazy margins involving the proximal diagonal artery (white arrow in a). |
The RCA ostial occlusion with downstream collateralization presents a diagnostic dilemma between congenital ostial atresia and an acquired mechanical occlusion. While robust retrograde collateralization of a normal calibre vessel suggests an in utero developmental origin[1], the absence of a pathognomonic ostial dimple or proximal blind ended stump, paired with adjacent sinus wall calcification and mural thickening, points toward an acquired etiology. A sinus of Valsalva aneurysm is defined morphologically as either the dilatation of one or more of the aortic sinuses located between the aortic valve annulus and the sinotubular junction, or a crescentic/tubular-shaped outpouching extending from the body or apex of a normally sized sinus of Valsalva.[2] The focal saccular outpouching observed in this patient meets the latter criteria. It is plausible that progressive distortion of the ostial interface driven by the synergistic effects of a localized sinus of Valsalva aneurysm, a severely acute take-off angle, and a low inter-arterial course could precipitate structural ostial obstruction or induce focal, accelerated atherosclerosis via altered local shear stress.[3] However, this mechanical hypothesis remains speculative, and the definitive etiology of this RCA ostial occlusion remains uncertain.
The morphology of the diagonal lesion is atypical for atherosclerotic coronary artery disease. Her clinical history was significant for hypertension and severe emotional distress (acute bereavement from the loss of a pet) at symptom onset, both of which are documented precipitants for spontaneous coronary artery dissection (SCAD). The imaging characteristics combined with patient history are suspicious for, but not diagnostic of, healed type III SCAD in which intramural hematoma and vessel wall remodelling may eventually manifest as residual focal stenosis.[4, 5] However, focal, concentric non-calcified plaque, a thrombus or vasospasm can mimic the angiographic appearance of a healed dissection on CorCTA, and because confirmatory intracoronary imaging was not performed, the definitive etiology of this diagonal stenosis remains indeterminate.[6]
Biochemical investigations revealed a normal fasting lipid profile, normal apolipoprotein-A, apolipoprotein-B and lipoprotein A levels. Her immunological profile was normal. A computed tomography (CT) arteriogram from brain to pelvis revealed normal aorta and its main branches with no evidence of tortuosity, aneurysms, stenosis, mural thickening or calcifications.
The patient was managed conservatively with guideline-directed medical therapy, including aspirin, carvedilol, an angiotensin receptor blocker, and eplerenone. As intracoronary imaging was not performed to definitively confirm SCAD, a moderate-intensity statin was initiated for secondary prevention, with plans for dose titration following follow-up CorCTA at 6 months to evaluate for lesion resolution. The patient was counselled regarding lifestyle modification, cardiac rehabilitation, and the avoidance of extreme physical and emotional stressors. Long-term management includes strict blood pressure control, regular clinical follow-up, serial TTE, and periodic thyroid function testing.
Perspective
This case was notable for the simultaneous manifestation of two distinct pathological processes occurring in the right and left coronary arterial system (Table 1). A stress-only CMR protocol was deemed sufficient in this patient as the presence of wall thinning, regional akinesia, and dense transmural LGE established a chronic, non-viable myocardial infarction, rendering a supplementary rest perfusion sequence clinically redundant.[7] This approach minimized scan time and contrast load while sufficiently elucidating tissue viability and the adequacy of the RCA collateral network under stress conditions.
Table 1. Role of CMR in evaluating two separate coronary artery abnormalities.
Role of MRI | Lesion 1: Diagonal artery stenosis | Lesion 2: RCA ostial occlusion |
Tissue characterization and localization | Delineated a transmural infarct involving the anterior segments (part of basal, entire mid and apical) and apical lateral segments, while sparing the adjacent basal and mid-anterolateral segments. | Demonstrated entirely preserved myocardium within the right coronary artery territory without evidence of infarction. |
Functional assessment of ischemic risk | A stress perfusion defect matched the zone of LGE with no peri-infarct inducible ischemia. Spared basal and mid anterolateral segments exhibited normal stress perfusion and normal wall motion. | Absence of inducible ischemia and normal segmental wall motion under stress confirmed that the retrograde collateral network adequately maintained myocardial perfusion. |
Clinical decision | The dense transmural scar indicated a low likelihood of functional recovery from intervention, while normal stress perfusion in the spared anterolateral segments indicated immediate revascularisation would offer no therapeutic benefit. | Documented perfusion adequacy via collateral channels supported the clinical decision that revascularisation was unnecessary.
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By demonstrating a chronic transmural infarction in one territory and adequately compensated collateral perfusion in the other under stress testing conditions, CMR provided the physiological evidence to pursue a conservative medical management strategy, avoiding potentially hazardous and low-utility invasive revascularization of both the lesions irrespective of their underlying atherosclerotic or non-atherosclerotic etiology.
However, given the patient’s moderate LV dysfunction (LVEF 32%) and a substantial scar burden (25%), close clinical follow-up is vital. Despite a negative stress study, findings from trials like ISCHEMIA and STICH emphasize that such high-risk substrates carry a persistent threat of adverse remodelling and sudden arrhythmic events.[8,9] Furthermore, there is an inherent risk of collateral-dependent perfusion failure under high biological demands.[10] This case highlights the utility of CMR in shifting clinical management from an anatomy-driven approach to a physiology-driven strategy when encountering coronary abnormalities of indeterminate origin. While invasive angiography and CorCTA delineated structural abnormalities, CMR clarified their functional significance in a single, non-invasive examination.
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References
- Pandey NN, Shaw M, Kumar S. Congenital ostial atresia of right coronary artery: an exceedingly rare anomaly diagnosed on CT angiography. BMJ Case Rep. 2019 Jul 23;12(7):e230377.
- Hanna MF, Malguria N, Saboo SS, Jordan KG, Landay M, Ghoshhajra BB, et al. Cross-sectional imaging of sinus of Valsalva aneurysms: lessons learned. Diagn Interv Radiol. 2017 Sep-Oct;23(5):339-346.
- Liu XP, Wang HJ, Gao JL, Ma GL, Xu XY, Ji LN, et al. Secondary coronary artery ostial lesions: Three case reports. World J Clin Cases. 2022 Jul 16;10(20):7045-7053.
- Gupta S, Meyersohn NM, Wood MJ, Steigner ML, Blankstein R, Ghoshhajra BB, et al. Role of Coronary CT Angiography in Spontaneous Coronary Artery Dissection. Radiol Cardiothorac Imaging. 2020 Nov 19;2(6):e200364.
- Zilio F, Mochen M, Muraglia S, Borghesi M, Zucchelli F, Todaro D, et al. Variability of time to healing of Spontaneous Coronary Artery Dissection assessed through coronary CT angiography. European Heart Journal. 2023 Nov;44(Supplement_2):ehad655-1396.
- Taheri M, Hayes SN, Bell MR, Raphael CE, Best PJM, Gulati R, et al. Spontaneous Coronary Artery Dissection or Coronary Atherosclerosis: Diagnostic Challenges in an Unclear Case. JACC Case Rep. 2026 Apr 22;31(16):107729.
- Swoboda PP, Matthews GDK, Garg P, Plein S, Greenwood JP. Comparison of Stress-Rest and Stress-LGE Analysis Strategy in Patients Undergoing Stress Perfusion Cardiovascular Magnetic Resonance. Circ Cardiovasc Imaging. 2023 Dec;16(12):e014765.Maron DJ, Hochman JS, Reynolds HR, Bangalore S, O’Brien SM, Boden WE, et al; ISCHEMIA Research Group. Initial Invasive or Conservative Strategy for Stable Coronary Disease. N Engl J Med. 2020 Apr 9;382(15):1395-1407.
- Velazquez EJ, Lee KL, Deja MA, Jain A, Sopko G, Marchenko A, et al; STICH Investigators. Coronary-artery bypass surgery in patients with left ventricular dysfunction. N Engl J Med. 2011 Apr 28;364(17):1607-16.
- Seiler C. Assessment and impact of the human coronary collateral circulation on myocardial ischemia and outcome. Circ Cardiovasc Interv. 2013 Dec;6(6):719-28.
Case prepared by:
Pranav Bhagirath, MD, PhD
Editorial Team, Cases of SCMR
Department of Cardiology, Libin Cardiovascular Institute / Foothills Medical Centre, Calgary, Canada