CASES OF THE WEEK – “Role of stress myocardial scintigraphy in the evaluation of post-PCI / stenting patients (A case of recurrent RCA stenosis with no ST-T changes on TMT)” by Dr ShekharShikare, Consultant & HOD, Nuclear Medicine
ROLE OF STRESS MYOCARDIAL SCINTIGRAPHY IN THE EVALUATION OF POST-PCI / STENTING PATIENTS (A CASE OF RECURRENT RCA STENOSIS WITH NO ST-T CHANGES ON TMT).
For many patients with multi-vessel disease, PCI is a definitive alternative to coronary artery by-pass graft (CABG). Complete revascularization remains a desirable goal, and a satisfactory outcome may be obtained with complete revascularization with PTCA or CABG.
Exercise testingis a widely used method particularly valuable in assessing cardiovascular status after the occurrence of a cardiac event or therapeutic interventions such as PCI. It may provide useful information on symptoms and functional capacity of the patient. The exercise testing, even if information from the electrical is poor diagnostic for myocardial ischemia with a sensitivity of 46% and a specificity of 77%. The use of stress nuclear imaging increases significantly the sensitivity to 87% and the specificity to 78%, while that of stress echocardiography imaging increases the sensitivity to 63% and the specificity to 87%. The lower sensitivity of the exercise ECG compared to imaging techniques in clinical practice is worsened further by inadequate stress yielding low exercise heart rates, the use of drugs that are known to influence test results, and the extent of disease in vessels other than those dilated. Furthermore, the exercise electrocardiogram does not permit the determination of location of the ischemia, nor does it accurately assess the extent of ischemia; these factors are often crucial in the clinical decision making after-PCI.
Although exercise testing has the advantage of widespread availability and relatively low cost, the higher test accuracy obtained by stress imaging provides greater advantages for clinical assessment of these patients. An additional advantage is that pharmacological imaging stress testing may be performed in patients who are unable to exercise or who have an uninterpretable electrocardiogram.
SPECT myocardial perfusion imaging (MPI) at different times from PCI have shown high level of sensitivity and specificity of nuclear imaging when compared to those of coronary angiography. The overall performance of SPECT-MPI for the detection of myocardial ischemia was 79% for both sensitivity and specificity. These values improve when MPI is performed later than 2 months after revascularization. The decreased specificity observed when MPI is performed prematurely after PCI was initially noted following PTCA and after coronary stenting. Indeed, MPI may be altered as a consequence of impaired flow reserve due to an epicardial coronary stenosis or, in the absence of coronary obstruction, as a consequence of an endothelial dysfunction and medial injury at the treated site or abnormal micro-vascular and resistive vessel function distal to the PCI site.
Case
48 years old gentleman with history of inferior wall myocardial infarction presented with unstable anginaà TMT positive for inducible
ischaemiaàCoronary AngiographyàMid RCA 90% StenosisàPTCA+Stenting done with good results.
Risk factorsà smoking, hypercholesterolemia and family history.
Five month later- Asymptomatic.
Ref. for stress myocardial perfusion imaging (MPI) for assessment of RCA status.
Bruce protocol – Exercise time 11.50 min / 12.9 mets / BP 180/70 achieved 95% of THR. No chest pain/ arrhythmias.
Stress MPI: Large area of reversible ischemia of moderate severity involving inferior and portion of inferio-lateral portion of the myocardium.
QGS->LVEF 68%, EDV 82 ml, ESV 27 ml, Stroke vol, 56 ml.
Subsequently underwent Coronary Angiography
RCAà Intra-stent blockageàCutting ballon angioplasty done.
Five months later- Asymptomatic.
Ref. for stress myocardial perfusion scan for assessment of RCA status.
Bruce protocol – Ex time 12.00 min, 12.9 mets, BP 210/70 and achieved 80% of THR. No chest pain/ arrhythmias.
Stress MPI à Combination of viable and scared myocardium with minimal stress induced ischemia in RCA territory.
The dominant abnormality within this distribution appears to be viability.
QGSà LVEF 66%, EDV 108 ml, ESV 37 ml, Stroke vol 72 ml.
One year later- Asymtomatic.
Ref. for stress myocardial perfusion scan for assessment of RCA status.
Bruce protocol – Ex time 12.30 min, 14.20 mets, 214/70 and achieved 84% of THR.No chest pain/ arrhythmias.
Stress MPIà Combination of viable and scared myocardium with considerable stress induced ischemia in RCA territory.
The dominant abnormality within this distribution is ischemia and viable tissue.
QGSà LVEF 67%, EDV 103 ml, ESV 34 ml, Stroke vol 69 ml.
Subsequently underwent Coronary Angiographyà restenosis of stent in Mid RCAà Rotablator atherectomy + Cypher stenting done.
Asymptomatic and doing well at present.
The relative prognostic information derived from MPI at one year after revascularization for patients with multivessel coronary artery disease reveals a strong correlation between detected ischemia on SPECT MPI scintigraphy and subsequent events. In patients with incomplete revascularization procedures, exercise SPECT MPI provides significant independent information concerning the subsequent risk of both hard and soft cardiac events, with a composite annualized event rate <2% for patients with a normal scan. SPECT MPI is able to provide incremental prognostic information after adjusting for clinical, angiographic, and exercise variables and is able to predict the occurrence of cardiac hard and soft events when separating patients according to the presence of myocardial ischemia and necrosis .Despite a low overall annual event rate of 1% per year, an abnormal MPI was significantly predictive of cardiac death or MI, whereas a normal MPI was associated with low risk.
Although complete revascularization remains a desirable goal in multivessel disease patients, incomplete revascularization strategy may be a preferred treatment strategy and a common clinical practice in many selected cases, when wisely chosen, because of its easier achievement and lower immediate risk. Among these incompletely revascularized patients, MPI is able to identify those patients with ischemic and viable myocardial regions, in which a “functionally complete revascularization” is needed to improve their outcome
ROLE OF STRESS MYOCARDIAL SCINTIGRAPHY IN THE EVALUATION OF POST-PCI / STENTING PATIENTS
(A CASE OF RECURRENT RCA STENOSIS WITH NO ST-T CHANGES ON TMT).
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ROLE OF STRESS MYOCARDIAL SCINTIGRAPHY IN THE EVALUATION OF POST-PCI / STENTING PATIENTS
(A CASE OF RECURRENT RCA STENOSIS WITH NO ST-T CHANGES ON TMT).
2
RROLE OF STRESS MYOCARDIAL SCINTIGRAPHY IN THE EVALUATION OF POST-PCI / STENTING PATIENTS
(A CASE OF RECURRENT RCA STENOSIS WITH NO ST-T CHANGES ON TMT).
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