Prediction of Cardiac Transthyretin Amyloidosis: Electrocardiographic Parameters and the Ratio of Posterior Wall Thickness to the Minimum QRS Complex Voltage in Limb Leads

<b>Background/Objectives</b>: Several predictive models have been proposed to estimate the probability of cardiac transthyretin amyloidosis (ATTR-CA). The aim of our study was to evaluate the usefulness of electrocardiographic parameters, as well as parameters consisting of a combination of myocardial thickness and QRS voltage, as potential predictors of ATTR-CA. <b>Methods</b>: In 2018-2025, 285 consecutive patients with suspected cardiac amyloidosis were evaluated, including blood tests, standard 12-lead electrocardiography, transthoracic echocardiography, and [^99mTc]Tc-DPD scintigraphy. <b>Results</b>: The ratio of posterior wall thickness to minimum QRS voltage in limb leads (PWT/minQRS ratio) as well as several ECG-derived parameters were independent predictors of ATTR-CA. In a comparison of ROC curves, PWT/minQRS ratio exceeded both the minimum and maximum voltage of QRS complexes in limb leads, demonstrated similar predictive value to TCAS and T-amylo scores, and had similar or superior predictive characteristics to posterior wall thickness. A cut-off of >3.3 for PWT/minQRS ratio was as accurate as the published cut-offs for TCAS score ≥6, T-amylo score ≥7, and posterior wall thickness ≥14 mm. In the subgroup of patients with myocardial thickness of at least 15 mm, PWT/minQRS ratio >3.3 was superior to posterior wall thickness ≥14 mm and T-amylo score ≥7 and had similar predictive value for ATTR-CA as TCAS score ≥6. <b>Conclusions</b>: In a cohort of undifferentiated patients referred for [^99mTc]Tc-DPD scintigraphy due to suspected cardiac amyloidosis, PWT/minQRS ratio showed strong predictive value for ATTR-CA, which was even more pronounced in the subgroup of patients with increased myocardial thickness.