Ayman A. Farag

The prognostic value of non-perfusion variables obtained during vasodilator stress myocardial perfusion imaging

Myocardial perfusion imaging (MPI) is an established diagnostic test that provides useful prognostic data in patients with known or suspected coronary artery disease. In more than half of the patients referred for stress testing, vasodilator stress is used in lieu of exercise. Unlike exercise, vasodilator stress does not provide information on exercise and functional capacity, heart rate recovery, and chronotropy, and ECG changes are less frequent. These non-perfusion data provide important prognostic and patient management information. Further, event rates in patients undergoing vasodilator MPI are higher than in those undergoing exercise MPI and even in those with normal images probably due to higher pretest risk. However, there are a number of non-perfusion variables that are obtained during vasodilator stress testing, which have prognostic relevance but their use has not been well emphasized. The purpose of this review is to summarize the prognostic values of these non-perfusion data obtained during vasodilator MPI.

Detection of right ventricular ischemia by SPECT myocardial perfusion imaging.

A 54-year-old man presented with acute bilateral lower extremity pain and weakness for 3 days thought to be ischemic in etiology. His past medical history included hypertension, hyperlipidemia, coronary artery bypass surgery, carotid stenting and ablation of atrial fibrillation. He underwent regadenoson stress gated SPECT myocardial perfusion imaging before planned vascular surgery. The rest ECG was abnormal (Figure 1, Top panel). The myocardial perfusion images showed extensive perfusion abnormalities involving 50% of the myocardium in the territories of all 3 major coronary arteries (Figure 1, Bottom panel, gray and color scales) with decreased ejection fraction of 28%. In addition, there was right ventricular (RV) ischemia and increased RV tracer uptake suggestive of pulmonary hypertension. The systolic pulmonary artery pressure by Doppler was 45 mmHg.

Prognostic value of silent myocardial infarction in patients with chronic kidney disease being evaluated for kidney transplantation

BACKGROUND Patients with advanced chronic kidney disease (CKD) have increased risk of myocardial infarction (MI). Silent MIs (SMIs) are common in CKD patients and carry increased mortality risk. The prevalence and prognostic value of SMI in advanced CKD has not been evaluated. METHODS We identified consecutive patients with advanced CKD who were evaluated for renal transplantation at the University of Alabama at Birmingham between June 2004 and January 2006. Clinical MI (CMI) was determined by review of medical records. SMI was defined as ECG evidence of MI without clinical history of MI. The primary end-point was a composite of death, MI, or coronary revascularization censored at time of renal transplantation. RESULTS The cohort included 1007 patients with advanced CKD aged 48±12years (58% men, 43% diabetes, 75% on dialysis). The prevalence of SMI and CMI was 10.7% and 6.7%, respectively. The only independent predictor of SMI was older age (odds ratio for age ≥50yrs. 2.32, p<0.001). During a median follow-up of 28months, 376 (37%) patients experienced the primary outcome (33% death, 2% MI, 5% coronary revascularization). In a multivariable adjusted Cox-regression model, both SMI (adjusted HR 1.58, [1.13-2.20], p=0.007) and CMI (adjusted HR 1.67 [1.15-2.43], p=0.007) were independently associated with the primary outcome. Further, both SMI (HR 2.37 [1.15-4.88], p=0.02) and CMI (HR 4.02 [1.80-8.98], p=0.001) were associated with increased risk after renal transplantation. CONCLUSIONS SMI is more common than CMI in patients with advanced CKD. Both SMI and CMI are associated with increased risk of future cardiovascular events.

Medical therapy for the treatment of myocardial ischemia

A 67-year-old man presented with exertional chest pain for 1 month, which was retrosternal in location, non-radiating, and relieved at rest. He has diabetes mellitus, hypertension, and hyperlipidemia. The physical examination was normal. He was referred for exercise myocardial perfusion imaging (MPI). He exercised for 6 minutes on the Bruce protocol. The test was stopped because of shortness of breath. The rest and exercise ECGs were normal. The exercise and rest SPECT images showed a large reversible perfusion abnormality involving 40% of the LV myocardium in the distribution of the left anterior descending artery (LAD) (Figure 1, first panel).The LV ejection fraction was preserved at 69%. The CT coronary angiogram showed a non-calcified plaque with 75% stenosis in the proximal segment of LAD (Figure 2). He was treated with aspirin, beta-blocker, statin, and long-acting nitrates. The symptoms improved on medical therapy with infrequent angina occurring less than once a month and relieved with sublingual nitroglycerin. The patient declined coronary interventions. A repeat exercise MPI was done 22 months later while on medical therapy (to same workload and exercise time). The perfusion abnormality was greatly reduced (Figure 1, panel 2). DISCUSSION

Incidentally found giant thymomas by SPECT myocardial perfusion imaging.

A 70-year-old man with hypertension presented for evaluation of intermittent chest pain. The physical examination was unremarkable except for morbid obesity. He underwent regadenoson gated Tc-99m sestamibi SPECT. The rest and stress ECGs were normal. The SPECT images showed normal myocardial perfusion with a left ventricular ejection fraction of 72% (Figure 1). There was a very large extracardiac mass in the anterior mediastinum seen on the tomographic and the raw rotating images (Figures 1, 2). Computed tomography confirmed the presence of a giant mass in the anterior mediastinum (Figure 3). The patient underwent left thoracotomy with excision of the mass. Histologic analysis revealed a 9.5 9 8 9 5.5 cm spindle cell tumor-rich in lymphocytes consistent with AB thymoma (Figure 4). The mass did not invade any of the surrounding structures. Adjuvant radiotherapy was deemed unnecessary and the patient did well postoperatively.

Non-diagnostic 18F-FDG PET myocardial viability studies in type-2 diabetic patients

INTRODUCTION F-FDG PET is a valuable functional imaging tool and the only FDA-approved technique for assessing viable myocardium in ischemic cardiomyopathy. It is based on the recognition that resting LV dysfunction may be reversible from myocardial hibernation/stunning, and not necessarily due to an irreversible myocardial scar. We report a case highlighting the pitfall of F-FDG PET myocardial viability study performed with the standardized protocol of oral glucose loading and intravenous regular insulin injections in a type-2 diabetic patient with non-diagnostic images.

Isolated right ventricular ischemia by SPECT myocardial perfusion imaging in a patient with coronary artery disease and pulmonary hypertension

A 66-year-old man with known coronary artery disease (CAD) (prior stenting of the proximal left anterior descending artery, LAD) and a pacemaker implant for syncope due to asystole presented with progressive dyspnea on exertion and orthopnea. The cardiac examination revealed a prominent pulmonic component of the second heart sound. The electrocardiogram showed sinus rhythm and right ventricular (RV) hypertrophy, right axis deviation, and ST/T changes (Figure 1). The chest x-ray showed cardiac enlargement and prominent pulmonary arteries suggesting pulmonary hypertension (PHT) (Figure 2). The two-dimensional transthoracic echocardiogram showed left ventricular (LV) hypertrophy with severe diastolic dysfunction but normal left ventricular ejection fraction (EF), moderate to severe tricuspid regurgitation, and dilated RV with EF of 20%-25%. Coronary angiography showed patent stent in the LAD, 95% distal left circumflex artery stenosis, 70% stenosis in the second marginal branch, and proximal occlusion of the right coronary artery (RCA) with left-to-right collaterals visualizing the distal vessel. Right heart catheterization revealed severe pulmonary hypertension (PHT), elevated pulmonary artery wedge pressure, and pulmonary vascular resistance (Table 1). He underwent exercise and rest gated SPECT myocardial perfusion imaging (MPI) using Tc-99m sestamibi to assess ischemic burden. The exercise findings are shown in Table 2. The patient had poor exercise tolerance. The gated SPECT images (Figure 3) revealed small LV size with normal perfusion pattern but flattened septum, dilated and hypertrophied RV, and a reversible RV perfusion defect.

Exercise-induced ST elevation with minimal ischemia by perfusion imaging

A 66-year-old African-American man with history of hypertension, hyperlipidemia, pulmonary embolism, tobacco use, and cocaine abuse over a year ago presented with resting chest pain that lasted 15 minutes and recurred after 45 minutes. The pain was sharp, left sided, and radiated to the left arm but without dyspnea, diaphoresis, or palpitations. The pain resolved spontaneously without intervention upon his arrival to the emergency department. His medications included atorvastatin, spironolactone, and warfarin. The physical examination was normal. The electrocardiogram and serial serum troponin levels were normal. He underwent exercise SPECT myocardial perfusion imaging (MPI) on the following day using stress/ rest protocol (Table 1). He exercised for 3:26 minutes and was asymptomatic during exercise but developed ST elevation during the first stage of Bruce protocol. The exercise was terminated and he complained of chest tightness during recovery requiring 3 sublingual nitroglycerin (NG) tablets (Table 2). The pain resolved and the ECG returned to baseline and he was asymptomatic. Rest ECG was normal while stress ECG showed ST elevation in V1-3 and aVL with reciprocal ST depression in inferior leads (Figure 1). Sestamibi was injected at peak exercise and just before NG administration. The images unexpectedly showed only mild and small anterior reversible defect (Figure 2). Parenthetically, the cath lab was activated, but since the patient was stable the images were acquired while awaiting transportation to catheterization laboratory. The left ventricular ejection fraction was 60% post stress and 62% post rest with no wall motion/ thickening abnormality. He underwent an emergency left heart catheterization which showed severe stenosis in the proximal right coronary artery (RCA), but the coronary circulation was codominant with no significant disease in the left anterior descending artery (LAD) or left circumflex artery (LCX) (Figure 3). The proximal RCA was stented.

Exercise induced polymorphic ventricular tachycardia during treadmill stress test

A 58-year-old man was scheduled for exercise MPI as part of pre-renal transplant evaluation. Prior to this, he exercised regularly on a treadmill and stationary bike for 20-40 minutes, 3-4 times weekly. His past medical history is significant for end stage renal disease (ESRD), atrial fibrillation, medication non-adherence, and coronary artery stenting of the left circumflex artery three years earlier (Figure 1). His home medications included carvedilol, atorvastatin, amiodarone, cinacalcet, hydralazine, lisinopril, and sevelamer. The cardiac examination was normal. The rest ECG is shown in Figure 2; the QT interval is normal. Prior 2dimensional echocardiogram had revealed EF of 4550%. The patient underwent a treadmill stress test with Bruce Protocol. The resting heart rate (HR) was 79 bpm and blood pressure (BP) was 85/35 mmHg. Two minutes into exercise, 1 mm ST depression was noted (Figure 3); but he was asymptomatic, and the BP was 111/65 mmHg. Five minutes into exercise, [2 mm ST depressions developed at a HR of 98 bpm (Figure 4) and again the patient denied any chest pain.

Incidental detection of abnormal (99m)Tc-sestamibi uptake in the sternum and ribcage from multiple myeloma by SPECT myocardial perfusion imaging.

A 66-year-old man with a past medical history of coronary artery bypass grafting, diabetes mellitus, hypertension, heart failure, and nonalcoholic steatohepatitis underwent regadenoson myocardial perfusion imaging (MPI) using Tc-sestamibi for evaluation of shortness of breath. Stress and rest ECGs were unremarkable. The images showed decreased perfusion in the inferolateral wall with no change from stress to rest consistent with a moderate-sized scar in the distribution of left circumflex coronary artery involving 15% of LV myocardium (Figure 1a). The left ventricular ejection fraction was 52%. Markedly abnormal radiotracer uptake in the sternum and the rib cage is noted on the tomographic (arrows in Figure 1a) and the rotating raw images (arrows in Figure 1b). The patient underwent bone marrow biopsy which confirmed the presence of multiple myeloma and subsequently was referred for bone marrow transplantation. DISCUSSION