Objectives Primary cardiac amyloidosis (CA) is associated with poor prognosis. However, the noninvasive diagnostic tools are limited. The aim of the study is to assess the utility of combined indexes of electrocardiography (ECG) and echocardiography (ECHO) in the diagnosis of primary CA.

Methods A total of 20 consecutive patients (7 men, mean age 50 ± 12 years) referred for endomyocardial biopsy (EMB) were included. Eleven of these patients (55%) confirmed primary CA, the rest of 9 patients were EMB negative and used for the control.

Results The voltage of S(V1) + R(V6) < 1.2 mV has a sensitivity of 91% and specificity of 89% for the identification of primary CA, yields the positive and negative predictive values of 91% and 89%, respectively. Among ECHO parameters, there were no significant differences between the 2 groups, except for left ventricular ejection fraction (47 ± 12% in primary CA vs 67 ± 11% in the control, P < 0.001). However, the combined indexes of ECG and ECHO parameters, including the ratio of R(I)/LVPW as well as R(V5)/LVPW and R(V6)/LVPW, were significantly lower in the patients with primary CA than the control. The ratio of R(I)/LVPW < 0.4 has the sensitivity of 91% and specificity of 100%, yields the positive and negative predictive values of 100% and 91%, respectively. The ratios of R(V5(6))/LVPW < 0.7 have the sensitivity of 91% and specificity of 89%, yield the positive and negative predictive values of 91% and 89%, respectively.

Conclusions Patients with clinically suspected primary CA, combined indexes of ECGs and ECHOs could be used as the noninvasive diagnostic tools.