Introduction: Left ventricular (LV) wall thickening and diastolic dysfunction on TTE without high voltage R wave on ECG to a diagnosis of cardiac amyloidosis (CA). However, amyloid sometimes invade right ventricle (RV), and left (LA) and right (RA) atria to cause ECG changes such as sick sinus syndrome (SSS), arrhythmia, and QRS axis deviation. Hypothesis: We hypothesized that sites of wall thickening and abnormal late enhancement (LE) on cardiac CT and MRI, suggesting amyloid invasion, correlated with cardiac rhythm and other ECG findings in patients with CA confirmed by biopsy. Methods: 26 patients (11 females) with suspected CA, showing LV wall thickening by TTE without a high voltage R wave, underwent cardiac CT. 5 patients (3 females, mean 73 years) were diagnosed with CA: complicated multiple myeloma, 2; senile ATTR (transthyretin) amyloidosis, 1; immunoglobulin light chain amyloidosis 1; and transthyretin mutation, 1. 4 patients underwent cardiac MRI. Results: 2 patients (cases 1 and 2) had SSS (junctional rhythm), 1 had atrial tachycardia, and the remaining 2 (cases 4 and 5) had a normal sinus rhythm. In case 1, ECG showed a left QRS axis deviation, no low voltage R wave and a mild LA load. Wall thickening in basal interventricular septum (IVS), LV inferior-posterior wall, LA on CT, LE in endocardium in whole LV, RV, and RA on CT, and LE in endocardium in whole LV, RV, LA, and IVS on MRI were observed. In case 2, ECG showed a normal QRS axis, no low voltage R wave, no LA load, wall thickening in whole LV, RV, LA, and IVS on CT, and unclear (CT) or no (MRI) LE. In case 3, ECG showed a normal QRS axis, with low voltage R wave, no LA load, wall thickening in LA and basal IVS on CT, LE in LA and basal IVS on CT, and LE in LA only on MRI. In case 4, ECG showed left QRS axis deviation, a low voltage R wave, and no LA load, wall thickening in LA and RV on CT, unclear LE on CT, and LE in whole LV, endocardium in RV, and whole IVS on MRI. In case 5, ECG showed a right QRS axis deviation, low voltage R wave, and a mild LA load, wall thickening in IVS, LV lateral wall, LV anterior wall, RA, RV outflow tract, and RA appendage, and no LE on CT (MRI not performed). Conclusions: The presence of wall thickening and abnormal LE in RV, LA, and RA in addition to LV on CT or MRI would be important which may influence ECG changes in patients with CA.