Spectrum of radionuclide perfusion study abnormalities in takotsubo cardiomyopathy

Myocardial flow reserve recovery in patients with Takotsubo syndrome: Insights from positron emission tomography

BACKGROUND

Coronary microvascular dysfunction (CMD) has been implicated in the pathogenesis of Takotsubo syndrome (TTS). Positron emission tomography (PET) plays a key role in the assessment of CMD through myocardial flow reserve (MFR). However, there is limited information on the temporal progression of MFR and its relationship to coronary artery disease (CAD) in TTS patients.

METHODS

This study evaluated patients with TTS who underwent cardiac catheterization and PET within one year of hospitalization. Patients were categorized into acute (≤10 days), subacute (11-30 days), and chronic (≥31 days) stages based on post-onset time of PET assessment. MFR values and prevalence of abnormal MFR (<2.0) were compared between stages. Temporal MFR changes in patients with obstructive CAD (≥70% stenosis by coronary angiography), non-obstructive CAD, and normal coronaries were compared.

RESULTS

Of the 88 patients studied (mean age 70; 96% female), 52 (59%) were in the acute, 17 (19%) in the subacute, and 19 (22%) in the chronic stage. Median MFR in the acute stage was 2.0 (1.5-2.3), with 58% of patients showing abnormal MFR. A significant time-dependent improvement in MFR was observed (P = 0.002), accompanied by a decreased prevalence of abnormal MFR (P = 0.016). While patients with normal coronaries showed significant MFR improvement over time (P = 0.045), patients with obstructive or non-obstructive CAD demonstrated no improvement across three stages (P = 0.346 and 0.174, respectively).

CONCLUSION

PET-derived MFR was impaired in TTS patients during the acute phase, with improvement suggesting potential recovery from CMD over time. The concurrent presence of obstructive CAD might impede this recovery process.

Role of nuclear cardiology in diagnosis and risk stratification of coronary microvascular disease

Coronary flow reserve (CFR) with positron emission tomography/computed tomography (PET/CT) has an important role in the diagnosis of coronary microvascular disease (CMD), aids risk stratification and may be useful in monitoring therapy. CMD contributes to symptoms and a worse prognosis in patients with coronary artery disease (CAD), nonischemic cardiomyopathies, and heart failure. CFR measurements may improve our understanding of the role of CMD in symptoms and prognosis in CAD and other cardiovascular diseases. The clinical presentation of CAD has changed. The prevalence of nonobstructive CAD has increased to about 50% of patients with angina undergoing angiography. Ischemia with nonobstructive arteries (INOCA) is recognized as an important cause of symptoms and has an adverse prognosis. Patients with INOCA may have ischemia due to CMD, epicardial vasospasm or diffuse nonobstructive CAD. Reduced CFR in patients with INOCA identifies a high-risk group that may benefit from management strategies specific for CMD. Although measurement of CFR by PET/CT has excellent accuracy and repeatability, use is limited by cost and availability. CFR measurement with single-photon emission tomography (SPECT) is feasible, validated, and would increase availability and use of CFR. Patients with CMD can be identified by reduced CFR and selected for specific therapies.

Takotsubo Cardiomyopathy in a Polytrauma Patient With Subarachnoid Hemorrhage

Takotsubo cardiomyopathy (TCM) is a sudden, transient myocardial stunning precipitated by severe emotional or physical stress. It is characterized by left ventricular apical ballooning and elevated cardiac enzymes without significant coronary artery stenosis. Stress-induced catecholamine surge has been proposed to be the likely mechanism of TCM. We report the case of a 23-year-old female who presented to the emergency department unconscious and in respiratory distress following a motor vehicle accident. The point-of-care ultrasonography showed prominent B lines in bilateral lung fields and a dilated inferior vena cava (IVC). An x-ray and computed tomography (CT) scan of the chest revealed bilateral diffuse ground glass opacities. A CT scan of the brain showed a subarachnoid hemorrhage (SAH). Electrocardiography (ECG) showed normal sinus rhythm, but troponin I was elevated. Echocardiography revealed left ventricular apical hypokinesia. The coronary angiogram was normal. A diagnosis of TCM with SAH was made. Appropriate emergent care was provided, and at follow-up, she made a complete cardiologic recovery. TCM is a puzzling condition in an emergency setting and accurate and timely diagnosis is imperative in the management. Early prevention of hypoxemia and maintenance of mean arterial pressure and cerebral perfusion pressure is critical in determining the long-term outcome of the patient in the setting of co-existing CNS pathologies.

A Review of Nuclear Imaging in Takotsubo Cardiomyopathy

Takotsubo cardiomyopathy or Takotsubo Syndrome (TTS) is a reversible left ventricular dysfunction syndrome that is increasingly being recognized. Recent advances in nuclear imaging have allowed us to study TTS in greater detail. We searched the PubMed and Medline databases and identified 53 publications with 221 patients reporting nuclear imaging findings in TTS. The age of the patients ranged from 17 to 87 years and were predominantly women (88.2%). The TTS variant was apical (typical) in 170 (76.9%), mid-ventricular in 23 (10.4%), and basal (reverse TTS) in 2 (0.9%). Cardiac perfusion was assessed using ^99mTc sestamibi (MIBI) SPECT, ^99mTc tetrofosmin SPECT, ²⁰¹Tl SPECT, ⁸²Rb PET, ²⁰¹Tl SPECT, and ¹³N ammonia PET. Additional studies used were ¹²³I MIBG SPECT, ¹²³I BMIPP SPECT, ¹⁸F FDG PET, ⁶⁷Ga citrate, and ¹¹C hydroxy-ephedrine. A perfusion defect was seen in 69 (31.2%), and an inverse perfusion–metabolism mismatch (normal or near-normal perfusion with absent myocardial metabolic activity) was seen in 183 (82.8%) patients. Nuclear imaging has a significant role in evaluating, diagnosing, and prognosticating patients with TTS. As nuclear imaging technology evolves, we will surely gain more insights into this fascinating disorder.