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CASE REPORT
Year : 2023 | Volume
: 24
| Issue : 4 | Page : 212-216
Abnormal resting myocardial contrast echocardiographic uptake: Clue of an ongoing acute coronary artery event
Roopesh Sai Jakulla1, Satya Preetham Gunta1, Angel López-Candales2
1 Department of Internal Medicine, University of Missouri Kansas City, Kansas City, MO, USA
2 Department of Internal Medicine, University of Missouri Kansas City; University Health Truman Medical Center, Kansas City, MO, USA
Correspondence Address:
Dr. Angel López-Candales
Division of Cardiovascular Diseases, University Health Truman Medical Center, Hospital Hill, University of Missouri-Kansas City, 2301 Holmes Street, Kansas City, MO 64108
USA
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/heartviews.heartviews_32_23
Abstract
Acute coronary syndromes (ACSs) present most frequently with chest pain, but angina equivalents such as dyspnea, diaphoresis, and fatigue are not uncommon. Atypical presentations are especially seen in women, the elderly, and diabetics. Cardiac evaluation using a transthoracic echocardiogram is almost always done before or immediately after someone undergoes left heart catheterization for ACS. It provides information valuable information regarding wall motion, left ventricular systolic function, diastolic function, right ventricular involvement, pulmonary pressures, incidental valvular disease, pericardial fluid, or any other unsuspected abnormality. We describe a novel case where an atypical presentation of ACS was suspected based on the lack of intravenous contrast administered, to enhance endocardial border resolution. The use of contrast during echocardiography has been used during stress protocols to assess microcirculation during perfusion assessment studies. However, we described a reduced uptake during the acquisition of resting myocardial echocardiogram images and it was very useful to direct therapy.
Keywords: Acute coronary artery event, coronary angiography, myocardial contrast, resting echocardiography
Introduction 
Despite improvements in diagnosis and treatment, cardiovascular diseases (CVDs) remain the leading cause of death globally, with an estimated 17.9 million deaths each year and in the United States. According to the latest American Heart Association statistics from 2020, 928,741 deaths were attributed to CVD.[1],[2]
In the United States, coronary artery disease (CAD) is responsible for approximately 610,000; thus it represents the leading cause of mortality.[2] In contrast, CAD is the third-leading cause of mortality worldwide, responsible for an estimated 17.8 million deaths annually.[3],[4],[5],[6]
Unfortunately, patients presenting with CAD have a range of symptoms and underlying risk factors. Furthermore, the relationship existing between patient-described symptoms, clinician conclusions, and subsequent clinical management, as well as outcomes, remains poorly described.
To that end, a secondary analysis of the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trials that included 9996 patients revealed that most patients presented with chest pain (47.2% substernal, 29.2% other), followed by dyspnea (14.9%), and other symptoms (8.7%).[7] Furthermore, patients complaining of dyspnea were older with a higher baseline risk of CVD.[7] The investigators of this trial concluded that among low-risk outpatients evaluated for CAD, the typicality of symptoms was not closely associated with higher baseline risk but was related to differences in processes of care and the prognostic value of a positive test.[7] In addition, adverse events were not associated with clinician risk estimates or symptoms alone. Therefore, physicians cannot simply rely solely on symptom presentation or clinician risk estimation when evaluating patients presenting with suspected acute coronary syndrome (ACS) due to CAD.[7]
To prove this point, we present a case where ACS was diagnosed based on a resting echocardiogram in which intravenous myocardial contrast was used. The results of this examination substantiated our clinical impression and played a crucial role in decision-making for a patient presenting with dyspnea, leading to a positive outcome.
Case Presentation An 84-year-old Vietnamese man with a history of type 2 diabetes mellitus and hypertension presented to our emergency department with 2 weeks of generalized weakness and 3 days of shortness of breath. On examination, his blood pressure was 206/126 mmHg, heart rate was 110 beats/min, and respiratory rate 18 breaths/min with an oxygen saturation of 91% on room air. Overall examination showed a frail male with dry mucus membranes. The rest of his examination was unremarkable, with no signs of decompensated heart failure.
An electrocardiogram (ECG) showed sinus rhythm with an isolated T wave inversion in lead V1. Laboratory studies revealed glucose 1,007 mg/dL, anion gap 21, serum osmolality 374 mOsm/kg, and hemoglobin A1c of 10.8%. High-sensitivity troponins were 321 and 956 (<4.9 pg/ml) 3 h apart. Computed tomography chest angiogram did not reveal pulmonary embolism but did show moderate calcification of coronary arteries. He was diagnosed with hyperglycemic hyperosmolar state (HHS) and a type 2 non-ST elevation myocardial infarction (NSTEMI). He was admitted to the critical care unit for further management.
A resting echocardiogram performed on arrival demonstrated a low normal left ventricular (LV) ejection fraction of 50%–55% with potential mild hypokinesis of the anteroseptal and apical anterior walls, including the apex. Injection of an intravenous ultrasound contrast agent (definity) was performed to enhance endocardial border definition by LV cavity opacification.
However, given his risk factors and lack of ECG changes, these wall motion abnormalities could have been old findings rather than new. In view of this dilemma, close attention to myocardial opacification revealed a lack of myocardial contrast uptake in these same regions, suggestive of abnormal myocardial perfusion, and thus provided further confirmation that these wall motion abnormalities were, in fact, new findings [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d. These perfusion abnormalities involving the anterior wall, apex, and anteroseptal walls were suggestive of the left anterior descending (LAD) artery with possible diagonal artery involvement.
Figure 1: (a) Parasternal long, (b) short axis, (c) four-chamber apical, and (d) two-chamber apical views are seen showing the left ventricle after the intravenous administration of contrast to enhance endocardial border resolution. Please note the lack of myocardial uptake in the areas demarcated by the white arrows. In the parasternal view (a), a lack of contrast is seen in the entire anteroseptal wall. In the short axis view (b), a lack of contrast is seen in the anterior wall. Lack of contrast in the apical four-chamber view (c), is localized to the apex while in the two-chamber view (d) is seen along the entire anterior wall. These perfusion abnormalities are suggestive of the left anterior descending artery with possible diagonal involvementBased on these IV myocardial contrast findings in the setting of dyspnea and rising troponin levels, an urgent left heart catheterization was performed, revealing a severe 80% stenosis of the mid-LAD artery and 80% stenosis of the proximal diagonal 2 (D2) artery [Figure 2]. The more proximal mid-LAD stenosis was somewhat hazy as well as the proximal D2 lesion.
Figure 2: (a) Coronary angiogram showing a large right coronary artery without any significant disease. (b) Coronary angiography of the left side shows two mid-left anterior descending artery lesions (white arrows) with a proximal diagonal two proximal stenosis (black arrow)Given the overall clinical condition of the patient and comorbid conditions, percutaneous coronary intervention with drug-eluting stent placement to both stenotic regions was accomplished without complications. An additional small caliber posterior descending artery with a distal right posterior descending artery (PDA) 80% stenotic lesion was left alone to be treated medically, given the small caliber nature of this distal stenosis.
The patient's symptoms improved after the intervention, and he was eventually discharged home after the resolution of HHS. The patient is currently doing well at 10 months of follow-up and is on carvedilol, losartan, atorvastatin, aspirin, and clopidogrel.
Discussion Echocardiography is the most utilized cardiac imaging tool, given its portability, low cost, and overall effectiveness in providing reliable and reproducible examinations of cardiac anatomy and function.[8] Despite significant advances in ultrasound transducer design, signal processing technology, and acquisition protocols, echocardiographic imaging remains technically difficult in at least 10%–15% of patients, likely due to obesity and lung disease.[9]
To circumvent these imaging limitations, echocardiographic contrast agents (ECAs) were developed. ECAs were first approved in 1990, and three second-generation ECAs are currently available in the United States, including Optison (perflutren protein-type A microspheres; GE HealthCare, Buckinghamshire, UK), Definity (perflutren lipid microsphere; Lantheus Medical Imaging, Billerica, MA), and Lumason (sulfur hexafluoride lipid-type A microspheres; Bracco Diagnostics Inc., Monroe Township, NJ).[9]
These ECAs consist of microbubbles with an outer protein or phospholipid shell that encapsulates a fluorocarbon gas. These agents are biologically inert and mimic the rheology of red blood cells in circulation.[10],[11] Given their excellent ultrasound scattering characteristics, these ECA agents improve the ability to discriminate between the blood pool and the endocardium and have been approved by the United States Food and Drug Administration for use in patients with suboptimal echocardiograms to opacify the LV chamber and to improve the delineation of the LV endocardial border.[12],[13],[14]
Since the approval of their use, ECAs have demonstrated invaluable utility in salvaging technically difficult studies in the intensive care unit, improving the accuracy of LV volume and ejection fraction determination, enhancing the ability to exclude LV thrombi, and improving the diagnostic accuracy of stress echocardiography.[15],[16],[17],[18],[19],[20],[21],[22]
Myocardial contrast echocardiography (MCE) is an imaging tool developed for the assessment of myocardial microcirculation. During MCE studies, intravenous infusion of an ECAs agent is administered. After the attainment of a steady state, the microbubbles are first destroyed with a high-energy ultrasound blast, and the rate of microbubble replenishment is then measured, which represents mean red blood cell velocity; thus, the patency of myocardial microcirculation.[23] The utility of MCE has been demonstrated in cases of acute myocardial infarction. Specifically, the area of injury and the success of reperfusion have been confirmed using MCE.[11] In fact, MCE has been to be clinically superior for the detection of ACS in the emergency department compared with routine evaluation.[24]
However, the utility of MCE has been limited to a determination of flow-related and myocardial perfusion abnormalities involving the LAD coronary artery stenosis.[25] Despite this limitation, MCE has been shown to define the region with no reflow, which approximates the total infarct size a day or two after hyperemia has abated, to determine the spatial extent of viable tissue postinfarction.[26],[27],[28],[29] Additionally, MCE can be used to define the extent of collateral perfusion during coronary occlusion and hence predict infarct size.[30]
To the utility of MCE in detecting coronary stenosis, detection has been studied with both infusions of dobutamine and dipyridamole.[31],[32] Dobutamine is a pharmacological agent that has both ionotropic and chronotropic effects depending on the dose.[33] In contrast, dipyridamole is an indirect coronary artery vasodilator, and its mechanism of action is mediated by blocking the cellular reuptake of endogenous adenosine.[34] Since the increase in myocardial blood volume assessments is greater with dobutamine than with dipyridamole, dobutamine is the preferred agent when performing MCE studies.[31],[32]
In our case, we were able to detect a lack of myocardial perfusion in the myocardial territories initially seen, suggesting that an acute LAD artery stenosis was causing the dyspnea and the elevation in cardiac markers. The novelty of our case resides in the utility of ECA during a resting echocardiographic test without the use of either dobutamine or dipyridamole.
Prompt identification of lack of myocardial perfusion was invaluable in proceeding with coronary angiography that was otherwise not considered optimal on presentation. However, since a significant amount of myocardium was involved and the territory was suggestive of compromise in LAD flow, the management plan was changed, and on coronary angiography, two severe stenoses were found. One involved the mLAD (80%), and the second an 80% proximal D2 lesion. Prompt percutaneous revascularization was successful with two drug-eluting stents, resulting in excellent postintervention thrombolysis in myocardial infarction (TIMI3) flow. The patient was discharged to home on dual antiplatelet therapy, beta-blocker, and angiotensin-converting enzyme inhibitors and has done remarkably well on follow-up with any additional cardiac event.
Conclusion The absence of chest pain can lead to diagnostic challenges in the diagnosis of ACS. An echocardiogram is a helpful tool and can aid in the diagnosis and risk stratification of ACS. An early invasive approach with angiography and revascularization in selected NSTEMI ACS patients is a potentially beneficial strategy, as it can prolong survival and reduce rehospitalization rates for angina.[35] Lack of myocardial contrast uptake in a resting echocardiogram is a potential marker for diagnosing atypical ACS, and more research is needed to find out if its prevalence in patients presenting with chest pain.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
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