Patients with HCM might have epicardial coronary artery disease, and many HCM patients with chest pain undergo stress perfusion imaging to detect ischemia. Treadmill, bicycle exercise, atrial pacing, dipyridamole, and adenosine were examined in this population. Defects, both reversible and fixed, were noted from 10% to 100% of the patients imaged (see (Table 3) from Keng et al.  for a summary). Most defects involve the septum but can occur in other walls. Although the general principles of SPECT interpretation apply to HCM patients, cardiologists should be cautious of “hot spots.” These have increased count activity and are most frequently noted in the septum in patients with asymmetric LVH. The increased count activity might be related to LVH and/or increased regional blood flow. Irrespective of the etiology of “hot spots,” if the tomographic slices are normalized to this area of increased count activity, regions adjacent to and distinct from the “hot spot” will appear relatively less intense, thereby creating spurious perfusion defects (Figure 8). Inaccurate image interpretation can be avoided by paying attention to the location and type of perfusion defects. The lateral wall is most frequently involved, and perfusion defects are usually fixed. Furthermore, on gated SPECT images, normal regional function will be noted despite the apparently reduced perfusion.