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ORIGINAL ARTICLE
INCREMENTAL PROGNOSTIC VALUE OF GATED
SPECT MYOCARDIAL PERFUSION SCANS WITH
DIPYRIDAMOLE STRESS IN PATIENTS WITH LEFT
BUNDLE BRANCH BLOCK
NOSHEEN FATIMA 1-2, MASEEH UZ ZAMAN 1,3, SYED ZAHED RASHEED 1, M ISHAQ 1, REHAN OMAR 1, SHOAIB Y ALI 1, DAD J BALCOH 1, JAVERIA BANO 1, ASIF WALI 1, KAWISH REHMAN 1,2 Objective: Gated single photon emission computerized
significantly lower in Group A (42 ±16) than Group B
tomography (GSPECT) myocardial perfusion imaging
(58 ±8) with significantly higher end diastolic and end
(MPI) has well validated incremental prognostic value.
systolic volumes (EDV, ESV) in Group A. At 18-24
The aim of this study was to find out the prognostic
months follow up, 09 (4.3%) non-fatal events were
value of abnormal dipyriodamole GSPECT MPI in
reported in Group B while in Group A it was 04 (2.9%,
patients with left bundle branch block (LBBB).
non-significant p values). Total 8 (5.90%) fatal MIs
were reported, all in Group A and none in Group B
Methods: This was a prospective study conducted at
(significant p values). Kaplan Meier survival plot for
Nuclear Cardiology Department of Karachi Institute of
non-fatal MI shows a similar event free survival in both
Heart Diseases (KIHD), Karachi from August 2010 till
groups with a Log Rank value 0.217 (non-significant
February 2011. Total 345 patients (135 with LBBB
p value) [Figure 2]. Kaplan Meier survival plot for fatal
comprised Group A and 210 without LBBB comprised
MI show significantly low event free survival for
Group B) with adequate dipyridamole GSPECT MPI
patients with LBBB (Group A) with a Log Rank value
were included. These patients were followed-up for 18-
10.552 (significant p value).
24 months (mean 20 ±3 months) for fatal or non-fatal
infarctions (MI).
Conclusions: We conclude that dipyridamole GSPECT
MPI provides important prognostic information in
Results: GSPECT scans were positive for abnormal in
patients with LBBB. LBBB group had lower LVEF
47/135 (35%) in Group A and in 90/210 (43%) in
which was a strong predictor of cardiac deaths while
Group B patients (non-significant p values). However,
perfusion parameters were predictors of non-fatal MIs
fixed perfusion defects were significantly higher in
in patients with or without LBBB.
Group A (27%) than Group B (15%) while reversible
defects were significantly higher in Group B (28%)
Key words: Gated SPECT, LBBB, Prognostic value,
than Group A (08%). Similarly incidence of transient
dipyridamole, fatal myocardial infarctions
ischemic dilatation (TID) was significantly higher in
Group B (16%) than Group A (02%). Mean sum stress
score (SSS) was higher in Group A (6 ±5) while mean
sum difference score (SDS) was higher in Group B (4
PJC 2012; 23: 25-31
±2). Left ventricular ejection fraction (LVEF) was
1. Nuclear Cardiology Department of Karachi Institute of Heart INTRODUCTION
2. Karachi Institute of Radiotherapy and Nuclear Medicine The incidence of left bundle branch block 3. Department of Radiology, The Aga Khan University Hospital (LBBB) in general population is low (0.6%) but almost 1/3rd of patients with chronic heart failure Address for Correspondence:
do have this abnormality.1 Presence of LBBB Dr. Maseeh uz Zaman
Associate Professor and Section Head Nuclear Medicine,
poses a challenge for diagnosis of ischemia due to Department of Radiology, AKUH, Karachi. presence of baseline ST-T changes which makes electrocardiogram (ECG) non-diagnostic at rest perfusion defects on stress images with or without and even during treadmill test.2-3 Non-ischemic transient ischemic dilatation (TID) visually, abnormal left ventricular ejection fraction (EF < cardiomyopathy, hypertensive heart disease, aortic 50%), abnormal wall motion, sum stress score valve disease and fibrosis of conduction fibers.4 [SSS], sum rest score [SRS] and sum difference Studies have shown that a higher incidence of score [SD] all >2. All patients/families were coronary artery disease (CAD) in patients with interviewed on telephone (18-24 months follow LBBB5 and 3-4 fold increased in mortality in up, mean 20 ±3 months) regarding MACE like patients with known CAD.6 Myocardial perfusion fatal myocardial infarction (MI) and non-fatal imaging (MPI) is a non-invasive imaging used for diagnosis and follow up of patients with CAD with good sensitivity but low specificity. This lowspecificity is caused by false positive septal Study Population: Study included 345
defects7 and specificity can be improved by using consecutive patients who were referred for vasodilators and gating.8 Gated single photon dipyridamole GSPECT MPI either for evaluation emission computerized tomography (GSPECT) of chest pain or risk factor assessment. Out of allows assessment of myocardial perfusion and these, 135 patients had LBBB on resting ECG (Group A) and 210 patients without LBBB (Group diagnostic and prognostic strength for patients B). In Group A, mean age of the cohort was 58 ± with CAD9. However, data is limited about the 9 years with a male: female ratio of 77: 58 (57%: prognostic value of pharmacological (vasodilator) 43%). Risk factor assessment in Group A revealed GSPECT in patients with LBBB with suspected that 93 (69%) were hypertensive, 49 (36%) were diabetic, 32 (24%) were dyslipidemic, 24 (18%)were smoker and positive family history for CAD The aim of this study was to find out the was found in 39 (29%) [Table1]. In Group B, prognostic value of abnormal dipyridamole mean age of the cohort was 56 ± 12 years with a male: female ratio of 126: 84 (60%: 40%). Riskfactor assessment in Group B revealed that 137 (65%) were hypertensive, 85 (40%) were diabetic,55 (26%) were dyslipidemic, 24 (11%) were Study Design, Site and Duration: This was
smoker and positive family history for CAD was found in 80 (38%) [all with non-significant p Cardiology Department of Karachi Institute of Heart Diseases (KIHD), Karachi, Pakistan fromAugust 2010 till February 2011. It was duly Acquisition Protocol: All patients underwent
approved by the ethical committee of the institute.
same day (rest-stress or stress-rest) myocardial We recruited 135 consecutive patients with LBBB Methoxy IsoButyl Isonitrile (MIBI). 10-15 mCi dipyridamole GSPECT scan for evaluation of of Tc-99m MIBI was administered intravenously known or suspected CAD. We also selected a for first study (rest in rest-stress or stress in stress- control group of 210 patients without LBBB rest protocol) and 25-30 mCi for second study (stress in rest-stress or rest in stress-rest protocol).
dipyridamole GSPECT. A positive GSPECT (with adequate dipyridamole intervention, i.e. increase acquisitions were performed using dedicated dual in pulse rate ≥10/min or drop of systolic BP ≥10 head cardiac (Cardio MD, Philips) gamma camera mmHg from baseline) was defined as presence of with low energy all purpose (LEAP) collimator, 32 projections around a 180 degree arc, a 64 x 64 study. A rise in ≥10 beats/minute (from baseline) matrix and 16 frames per cardiac cycle. Image or drop of ≥10 mmHg of systolic blood pressure reconstruction and LV functional parameters (EF, with or without symptoms or ST changes were considered as adequate response to dipyridamole.
contemplated by using commercially available Astonish® and Autoquan® software packages dipyridamole infusion. Intravenous aminophylline respectively. An EF ≥ 50%, ESV ≤ 70 ml and WM (75-125 mg) was given to all patient 2-3 minutes score of zero (in a 17 segment model) were after radiotracer to antagonize the effect of considered normal. Similarly, GMPI with SSS, SRS and SDS <2 were considered as normal. Statistical Analysis: Comparisons between
Stress Protocol: Dipyridamole intervention
patient groups were performed using student-t test was performed intravenously at a rate of 0.567 for continuous variables and the X2 test for mg/kg for 4 minute in all patients. Tea, coffee and categorical variables. Continuous variables were xanthine derivatives were stopped 24 prior to described by mean ± standard deviation (SD).
Table-1: Demographic comparison of both groups (Group A=with LBBB, Group; B=without LBBB)
*p<0.05SD= Standard DeviationMPS=Myocardial Perfusion ImagingTID=Transient Ischemic DilatationSSS=Sum Stress ScoreSDS=Sum Difference Score Figure-1: Comparative fatal and non-fatal events among both groups
Figure-2: Kaplan Meier Survival Plot for Non-Fatal Myocardial Infraction among both groups (Group A=LBBB; Group
B=without LBBB) in 18-24 months follow up.
Kaplan-Meier cumulative survival analysis for compared by the Logrank test. Statistical major cardiac events like fatal and non-fatal MI significance was defined as P<0.001.
Figure-3: Kaplan Meier Survival Plot for Fatal Myocardial Infraction among both groups (Group A=LBBB; Group B=without LBBB) in 18-24 months follow up significantly higher end diastolic and end systolicvolumes (EDV, ESV) in Group A (Table 1). perfusion findings in 47/135 (35%) in Group A At 18-24 months follow up, 09 (4.3%) non- and in 90/210 (43%) in Group B patients (non- fatal events were reported in Group B while in significant p values). However, fixed perfusion Group A it was 04 (2.9%). These non-fatal events defects were significantly higher in Group A included hospital admissions with chest pain (27%) than Group B (15%) while reversible culminated in revascularization 07 patients (05 in defects were significantly higher in Group B Group B and 02 in Group A). Total 8 (5.90%) fatal (28%) than Group A (08%). Similarly incidence MI were reported in the studied population (all in of TID was significantly higher in Group B (16%) Group A and none in Group B) [Figure 1). Kaplan than Group A (02%). Mean SSS was higher in Meier survival plot for non-fatal MI show a similar Group A (6 ±5) indicting extent of CAD while event free survival in both groups with a Log Rank mean SDS was higher in Group B (4 ±2) which value 0.217 (non-significant p value) [Figure 2].
shows higher ischemia burden in patients without Kaplan Meier survival plot for fatal MI show LBBB (Group B). Left ventricular function significantly low event free survival for in patients parameters like LVEF (%) was significantly lower with LBBB (Group A) with a Log Rank value in Group A (42 ±16) than Group B (58 ±8) with 10.552 (significant p value) [Figure 3].
DISCUSSION
statistically non-significant) non-fatal events inGroup B. These data are in accordance with a large Gated SPECT with perfusion and functional published trial by Cedar Senai investigators16 parameters has an established incremental which revealed LVEF<45% as significant diagnostic and prognostic value in general predictor of mortality while LVEF>45% had lower population; however, data is scarce about its role mortality rate irrespective of severity perfusion in LBBB group. In this study abnormal GSPECT abnormalities on GSPECT. They also found that scans were non-significantly higher in Group B perfusion variables are powerful in predicting than Group A and most likely due to biased worsening of coronary disease. In our study mean sampling. In Group A, incidence of fixed perfusion SSS and SDS were in mild to moderate range in defects was significantly higher and this could be both groups and studies have shown differential justified due to known anteroseptal defects risk stratification of lower score for non-fatal associated with LBBB. Various mechanism have events and correlation of higher scores with fatal been proposed for this false positive finding like impaired diastolic flow to septum due to itsdelayed contraction,10 short diastolic filling at higher rate11 and decrease baseline and systole provides important prognostic information in septal thickness with normal perfusion (partial LVEF which was a strong predictor of cardiac dipyridamole stress and gating to avoid it but deaths while perfusion parameters were predictor studies have shown that these measures can reduce of non-fatal MIs in patients with or without LBBB.
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