Formulaic quantification of echocardiographic left atrial volume.

INTRODUCTION

The association between increasing severity in abnormal atrial depolarization and left atrial (LA) volume derived by transthoracic echocardiogram (TTE) has been described through the following regression formula: LA end-systolic volume index (LAVI [milliliter]) = 8.0 + 0.2 (P-wave duration [millisecond]) (r = 0.47; P = .0002). However, prospective assessment of this formula has not been validated among inpatients outside the institution where it was first derived.

METHODS

We prospectively obtained 12-lead electrocardiograms (ECGs) and TTEs on consecutive inpatients who were scheduled for nonemergent echocardiographic assessment. P waves were assessed independently to the nearest 10 milliseconds for application of the formula with a Bland-Altman plot. P-wave durations were obtained specifically from lead II and also from the any lead that yielded the widest measurement.

RESULTS

After excluding those with poor ECG tracing and TTE images, 72 patients were studied. We found a strong formulaic correlation with LAVI by TTE when maximal P-wave measurements were obtained from any ECG lead (r = 0.67; P < .0001) and more so, when restricted only to lead II (r = 0.89; P < .0001). Correlation was strongest when there was no or minimal difference between P-wave measurements in lead II and all other leads (r = 0.84; P < .0001 for no difference vs r = 0.67; P < .0001 for 60-millisecond difference). The Bland-Altman plot showed good agreement of LAVI assessment using the formulaic estimation when compared to TTE measurements derived by Simpson's rule (coefficient of reproducibility for 2 SD equivalent to 8.8% for lead II and 11.4% for any lead).

CONCLUSION

There is good agreement and correlation between formulaic estimation and that of TTE for LAVI among inpatients. Such quantification of LA size not only serves as an indirect asset that could perhaps supplement TTE measurements in certain circumstances but also can facilitate risk stratification of patients.