Dynamic QT/RR relation in patients with acute myocardial infarction

Abstract

The dynamic relationship between the QT and RR intervals (QT/RR relation) in 13 patients with Acute Myocardial Infarction (AMI) was assessed by sequential 24-hour Holter ECG (Electrocardiogram) monitoring, and compared with 11 normal subjects (control). A computer algorithm for automatic measurement of the QT interval (an interval from the QRS onset to the T wave apex) was employed to obtain the slope of the linear regression in the ECG data plots (QT/RR slope) and its correlation coefficient (r). The QT/RR slope and r values in the control subjects were 0.14 +/- 0.03 (mean +/- SD (Standard Deviation), n = 11) and 0.71 +/- 0.10 (n = 11), respectively. At an acute phase of the AMI patients (one day after the onset), the QT/RR slope (0.17 +/- 0.05, n = 13) was higher, whereas r (0.44 +/- 0.18, n = 13) was lower than controls. At a recovery phase of the AMI patients (15 days after the onset), the QT/RR slope returned toward controls (0.11 +/- 0.07, n = 13), whereas r remained at the lower level (0.36 +/- 0.33, n = 13). Such phase-dependent alterations in the QT interval dynamics may help to clarify the complex arrhythmogenic substrates in patients with AMI.

連続24時間ホルター心電(ECG)計を使用して急性心筋梗塞(AMI)患者13名においてQT間隔とRR間隔の動的な関連性(QT/RR関連)を検討し、正常被験者11名(対照群)と比較した。QT間隔(QRS発生からT波先端までの間隔)自動測定用のコンピュータアルゴリズムを使用して、ECGデータプロットの線形回帰の勾配(QT/RR勾配)およびその相関係数(r)を得た。対照群のQT/RR勾配およびr値はそれぞれ0.14±0.03(平均±標準偏差(SD)、n=11)および0.71±0.10(n=11)であった。AMI患者群の急性期(発症1日後)では、対照群に比べQT/RR勾配が大きく(0.17±0.05、n=13)、r値は低かった(0.44±0.18、n=13)。AMI患者群の回復期(発症15日後)では、QT/RR勾配は対照群ど同等まで回復したが(0.11±0.07、n=13)、r値は低レベルに留まった(0.36±0.33、n=13)。QT間隔動力学におけるこの病期依存的な変化は、AMI患者における複雑な不整脈原因基質の解明に役立つと思われる。