Increased stress right ventricular activity on dual isotope perfusion SPECT
A sign of multivessel and/or left main coronary artery disease
Kim A. Williams, MD, FACCa and
Candace M. Schneider, BSa
a Departments of Medicine (Cardiology) and Radiology (Nuclear Medicine), The University of Chicago, Chicago, Illinois, USA
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Figure 1 Examples of the normal and increased right ventricular (RV) activity are shown. (A) Mid-ventricular horizontal long axis and short axis images are shown in a normal participant at exercise (above) and rest (below). There is a normal degree of RV activity at stress (arrow). The resting scan shows normal RV activity, but with some splanchnic thallium-201 activity that limits the evaluation of the counts in the inferior aspect of the RV. (B) These images are from a patient with left main and three-vessel CAD, but only mild CAD in the proximal right coronary artery. The resting images are normal. With exercise, there were only mild reversible perfusion abnormalities (anterior, inferolateral, lateral-apical, lateral), but exercise-induced ischemic cavity dilatation, consistent with more global ischemia. The relative RV activity was normal at rest, but increased markedly with exercise, consistent with global LV ischemia, preserved RV perfusion, and most possibly an increase in pulmonary pressures with stress. (C) These images were obtained on an elderly patient with an ostium secundum atrial septal defect, severe pulmonary hypertension and marked RV hypertrophy. The increased RV activity is present at rest and stress (RV:LV activity indexes of 0.51 and 0.53, respectively) with a normal exercise to resting ratio of 1.045. CAD = coronary artery disease; LV = left ventricular; RV = right ventricular.
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Figure 2 Mean values of exercise-to-rest ratios are shown for each of the subgroups of patients with and without coronary artery disease. There was marked increase in RV:LV ratio from the resting thallium-201 to exercise Tc-99m-sestamibi or tetrofosmin in the group of patients with LM or LME CAD and less stenosis of the proximal right coronary artery (*p < 0.001 vs. normals and other CAD groups). CAD = coronary artery disease; Cath = percent diameter stenosis on cardiac catheterization; CX = circumflex CAD; LAD = left anterior descending CAD; LM = left main CAD; LME = "left main equivalent" proximal LAD and CX CAD; LV = left ventricular; RCAp = proximal right CAD; RV = right ventricular; 1 or 2VD = single- or double-vessel CAD.
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Figure 3 Scatterplots of individual data points of rest and exercise RV:LV perfusion ratio for each patient in the study are shown, grouped by CAD anatomic features or normalcy. The RV:LV perfusion ratios are highly correlated (p < 0.0001) for each subgroup of patients, except for the patients with LM CAD or LME CAD and a lesser degree of (or absent) RCAp disease (A), in whom the exercise RV:LV index is much greater than the resting RV:LV, with r = 0.39, p = NS. The criteria of an exercise RV:LV ratio of >0.42 and exercise to resting RV:LV index ratio of >1.2 was met by the majority of this group, but by no one with a proximal RCA lesion as their tightest stenosis. These criteria were met by only three patients with no significant CAD on Cath and only one patient in the normalcy group (B). The frequency of this finding increased as the degree of CAD increased (C). Abbreviations are the same as in Figure 2.
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Figure 4 The frequency of an increased RV:LV ratio from rest to exercise, defined as an exercise RV:LV ratio of >0.42 and exercise-to-resting RV:LV index ratio of >1.2, is depicted for each of the patient subgroups described in Figures 1–3. Patients with >70% LM or LME CAD but less (or absent) RCAp disease had a much greater frequency of this finding (93%) than did other groups (*p < 0.0001 vs. normals and other groups). Patients with milder degrees of LM or three-vessel CAD without a tighter proximal RCA had an intermediate frequency of this finding (30%). Abbreviations are the same as in Figures 2 and 3.
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