Left bundle branch block causes relative but not absolute septal underperfusion during exercise

Aims Left bundle branch block (LBBB) often causes septal perfusion defects in radionuclide myocardial perfusion imaging using exercise (Ex) but rarely using vasodilator stress. We studied whether this is due to an underlying structural disease inherent to spontaneous LBBB or whether it is also found in temporary LBBB induced by right ventricular pacing (PM) indicating a functional rather than a structural alteration. Methods and results Regional myocardial blood flow (MBF) at rest and at Ex was measured with(15)O-H(2)O and PET in 10 age-matched healthy volunteers (controls), 10 LBBB patients and 10 PM patients with right ventricular pacing off and on (PM off and PM on). Although at Ex septal MBF tended to be higher in LBBB than in controls (3.04 +/- 1.18 vs. 2.27 +/- 0.72 mL/min/g; P= ns), the ratio septal/lateral MBF was 19% lower in LBBB than in controls (P < 0.05). Similarly, switching PM on at Ex decreased the ratio septal/lateral MBF by 17% (P < 0.005). Conclusion The apparent septal perfusion defect in LBBB is mainly due to a relative lateral hyperperfusion rather than to an absolute septal flow decrease. This pattern seems to be reversibly inducible by right ventricular pacing, suggesting a functional rather than a structural alteratio

(13)N-ammonia myocardial perfusion imaging with a PET/CT scanner: impact on clinical decision making and cost-effectiveness

PURPOSE: The purpose of the study is to determine the impact of 13N-ammonia positron emission tomography (PET) myocardial perfusion imaging (MPI) on clinical decision making and its cost-effectiveness. MATERIALS AND METHODS: One hundred consecutive patients (28 women, 72 men; mean age 60.9 +/- 12.0 years; range 24-85 years) underwent 13N-ammonia PET scanning (and computed tomography, used only for attenuation correction) to assess myocardial perfusion in patients with known (n = 79) or suspected (n = 8) coronary artery disease (CAD), or for suspected small-vessel disease (SVD; n = 13). Before PET, the referring physician was asked to determine patient treatment if PET would not be available. Four weeks later, PET patient management was reassessed for each patient individually. RESULTS: Before PET management strategies would have been: diagnostic angiography (62 of 100 patients), diagnostic angiography and percutaneous coronary intervention (PCI; 6 of 100), coronary artery bypass grafting (CABG; 3 of 100), transplantation (1 of 100), or conservative medical treatment (28 of 100). After PET scanning, treatment strategies were altered in 78 patients leading to: diagnostic angiography (0 of 100), PCI (20 of 100), CABG (3 of 100), transplantation (1 of 100), or conservative medical treatment (76 of 100). Patient management followed the recommendations of PET findings in 97% of the cases. Cost-effectiveness analysis revealed lower costs of 206/patient as a result of PET scanning. CONCLUSION: In a population with a high prevalence of known CAD, PET is cost-effective and has an important impact on patient management

Role of attenuation correction to discriminate defects caused by left bundle branch block versus coronary stenosis in single photon emission computed tomography myocardial perfusion imaging.

PURPOSE: To define the impact of attenuation correction (AC) on interpretation of perfusion abnormalities induced by left bundle branch block (LBBB) in myocardial perfusion imaging (MPI) and single photon emission computed tomography (SPECT). METHODS: Thirty-six patients with spontaneous and 12 with pacemaker (PM)-induced LBBB (mean age 68.6 +/- 9.7) underwent gated 1-day adenosine stress/rest Tc-99m tetrofosmin SPECT on a hybrid SPECT-CT dual-head detector camera with Hawkeye facility (Infinia, GE Healthcare, Milwaukee, WI). Images were analyzed using iterative reconstruction (IR) and AC by computerized tomography (IR-AC) and compared with filtered back protection (FBP) as a standard of reference. Defect extent and severity for the anterior, septal, apical, inferior, and lateral regions were assessed by computerized analysis. The combination of septal with anterior and/or apical perfusion defects was attributed to the typical LBBB-induced pattern. RESULTS: LBBB caused a typical perfusion pattern in 24 patients with spontaneous and in 10 with PM-induced LBBB, whereas MPI was normal in 14 patients. FBP revealed a partial reversibility of anterior (spontaneous LBBB) and apical-septal (spontaneous and PM-induced LBBB) defect severity. By IR-AC, LBBB caused comparable anteroseptal reversible perfusion defects (P < 0.05) but fixed apical defects. Apical-septal defect severity was higher and defect extent was larger in IR-AC compared with FBP (both P < 0.05). Defect extent was unchanged between rest and stress for both reconstructions. CONCLUSIONS: Spontaneous and PM-induced LBBB often induces typical perfusion defects in MPI at stress, partly reversible at rest. With IR-AC this typical pattern is more pronounced and less reversible, strengthening the confidence to discriminate such findings from ischemia

Left bundle branch block causes relative but not absolute septal underperfusion during exercise

Aims Left bundle branch block (LBBB) often causes septal perfusion defects in radionuclide myocardial perfusion imaging using exercise (Ex) but rarely using vasodilator stress. We studied whether this is due to an underlying structural disease inherent to spontaneous LBBB or whether it is also found in temporary LBBB induced by right ventricular pacing (PM) indicating a functional rather than a structural alteration. Methods and results Regional myocardial blood flow (MBF) at rest and at Ex was measured with(15)O-H(2)O and PET in 10 age-matched healthy volunteers (controls), 10 LBBB patients and 10 PM patients with right ventricular pacing off and on (PM off and PM on). Although at Ex septal MBF tended to be higher in LBBB than in controls (3.04 +/- 1.18 vs. 2.27 +/- 0.72 mL/min/g; P= ns), the ratio septal/lateral MBF was 19% lower in LBBB than in controls (P < 0.05). Similarly, switching PM on at Ex decreased the ratio septal/lateral MBF by 17% (P < 0.005). Conclusion The apparent septal perfusion defect in LBBB is mainly due to a relative lateral hyperperfusion rather than to an absolute septal flow decrease. This pattern seems to be reversibly inducible by right ventricular pacing, suggesting a functional rather than a structural alteration

Impact of CT attenuation correction on the viability pattern assessed by (99m)Tc-tetrofosmin SPECT/ (18)F-FDG PET

SPECT myocardial perfusion imaging (MPI) is commonly used for comprehensive interpretation of metabolic PET FDG imaging in ischemic dysfunctional myocardium. We evaluated the difference in scan interpretation introduced by CT attenuation correction (CTAC) of SPECT MPI in patients undergoing viability characterization by (99m)Tc SPECT MPI/PET FDG. In 46 consecutive patients (mean age 64, range 36-83 years) with dysfunctional myocardium, we analyzed viability from combined SPECT MPI and PET FDG scanning without attenuation correction (NC) and with CTAC for SPECT MPI. FDG uptake was classified in groups of percent uptake using the segment with maximum tracer in SPECT perfusion uptake as reference. Viability patterns were categorized as normal, mismatch, mild match and scar by relative comparison of SPECT and PET. Applying CTAC introduced a different reference segment for the normalization of PET FDG study in 57% of cases. As a result, the flow-metabolism pattern changed in 28% of segments, yielding a normal, mismatch, mild match and scar pattern in 462, 150, 123, and 47 segments with NC and 553, 86, 108, and 35 with CTAC, respectively (P = 0.001). Thus, by introducing CTAC for SPECT MPI 25% of segments originally classified as scar were reclassified and the number of normal segments increased by 20%. Introducing CTAC decreased by 54% the number of patients with possible indication for revascularization, from 26/46 to 12/46 (P < 0.001). Different interpretation of myocardial viability can be observed when using CTAC instead of NC SPECT MPI as reference for PET FDG scans

Accuracy of quantitative coronary angiography with computed tomography and its dependency on plaque composition: Plaque composition and accuracy of cardiac CT

Objective: To determine the impact of plaque composition on accuracy of quantitative 64-slice computed tomography coronary angiography (CTCA). Methods: The institutional review board approved this study; written informed consent was obtained from all patients. One hundred consecutive patients (42 women, mean age 64.6 +/- 9.4 years, age range 39-87 years) underwent CTCA and invasive quantitative coronary angiography (QCA) to determine (a) the diagnostic accuracy of CTCA for the detection of significant stenosis (diameter reduction of >/=50%), and (b) the accuracy of stenosis grading. In CTCA stenosis severity was graded in 10% steps and evaluated separately for calcified and non-calcified coronary lesions using Pearson-linear-regression analysis, Bland/Altman-analysis (BA), and Mann-Whitney-U-test. Results: In 60/100 patients 139 significant coronary artery stenoses were identified with QCA. On a per-segment analysis, sensitivity of CTCA was 75.5%, and specificity was 96.6% (positive predictive value: 72.9%, negative predictive value: 97.0%). Quantification of stenosis grading correlated moderately between methods (r = 0.60; P < 0.001), with an overestimation by CTCA of 5.5% (BA limits-of-agreement -29 to 39%). BA limits-of-agreement were greater in calcified lesions (-29.2 to 45.6%; mean error 8.2%) than in non-calcified lesions (-25.9 to 30.2%; mean error 2.2%) and differed significantly (P < 0.05). Conclusions: Diagnostic accuracy of CTCA is high, however agreement for quantitative lesion severity assessment between CTCA and QCA is moderate for calcified but superior for non-calcified lesions