Increasing Daily Physical Activity and Its Effects on QTc Time in Severe to Very Severe COPD: A Secondary Analysis of a Randomised Controlled Trial

Figures & data

Figure 1. The length of the QT interval was obtained by identifying the QRS onset and the point at which the downward slope of the T wave returns to baseline.

Figure 2. Study flow.

Figure 3. Boxplots showing QTc at baseline and 3 month follow-up visit in Non-Improver (difference from baseline to end of study -13 ms) and Improver (difference from baseline to end of study -27 ms), p-value for effect adjusted baseline QTc = 0.16. Data are mean (SD). Solid gray line: mean.

Table 1. Patients’ characteristics.

	Non-improver (NG)	Improver (IG)
N	36	23
Age, yr	68 (8)	63 (9)
Sex, male/female	25/11	16/7
BMI, kg/m^2	24.8 (4)	25.9 (4)
Smoking, current/ former /never	4/32/0	3/20/0
Smoking, pack-years	56 (33)	58 (33)
COPD Risk Group, n A B C D	0 0 23 13	0 0 18  5
FEV1, post BD, L	0.94 (0.33)	1.07 (0.26)
FEV1 post BD, % pred.	33 (10)	36 (8)
FEV1 / FVC post BD, %	39(8)	40(5)
QTc-Time, ms	441 (36)	442 (42)
QTc Prolongation, yes/no	21/15	10/13
CVD/Arrhythmia , yes/no	12/24	8/15
QT prolonging drugs, yes/no	13/25	15/6
Daily step count, n (max-min)	2719 (12869-196)	3642 (15082-338)

Data are mean (SD) or absolute numbers; BMI: body mass index; FEV₁: forced expiratory volume in 1 s; BD: Bronchodilator; QTc – Time: QT-interval corrected for heart rate with Barzett formula; QTc Prolongation ≥450 ms in males or ≥460 ms in females; CVD: cardiovascular diseases; Medication QT Prolongation; medication; listed as QT drugs with potential of QT prolongation (www.qtdrugs.org).

Table 2. Changes of QTc (Barzett) stratified according to the course of PA.

	Non-Improvers n = 8			Improver n = 21			Mean group difference (95%CI)	Effect adjusted for baseline QTc	P adjusted for baseline QTc
	Baseline	Follow-up	Change	Baseline	Follow-up	Change
QTc, ms	441 (36)	428 (41)	−13 (39)	442 (42)	416 (53)	−27 (33)	−14 (-33 to −6)	−13 (-33 to 6)	0.16

Data are mean (SD), CI = Confidence interval; Non-Improver: Participants ≤ 15% enhancement of daily steps; Improver: Participants ≥ 15% enhancement of daily steps; QTc (Bazett): QT-interval corrected for heart rate with Barzette formula.