Does heart rate variability correlate with long-term prognosis in myocardial infarction patients treated by early revascularization?

Table 1 Main data of patients, reported for the whole group and for patients with ST-elevation myocardial infarction and non-ST-elevation myocardial infarction

	All patients (n = 326)	STEMI (n = 208)	NSTEMI (n = 118)	P1	P2
Age, yr	63.5 ± 12.1	61.3 ± 12.5	67.4 ± 10.4	< 0.001
Male, n (%)	261 (80)	171 (82)	90 (76)		0.197
History and cardiovascular risk factors
Known diabetes, n (%)	82 (25)	45 (22)	37 (31)		0.055
Abnormal glucose metabolism, n (%)	106 (32)	68 (33)	38 (32)		0.733
Hypertension, n (%)	238 (73)	134 (64)	104 (88)		< 0.001
Smoking habit, n (%)	106 (32)	81 (39)	25 (21)		0.001
Family history, n (%)	179 (55)	111 (53)	68 (58)		0.367
Previous CABG, n (%)	26 (8)	7 (3)	19 (16)		< 0.001
Previous PCI, n (%)	43 (13)	13 (6)	30 (25)		< 0.001
Previous AMI, n (%)	60 (18)	21 (10)	39 (33)		< 0.001
Previous stroke, n (%)	11 (3)	5 (2)	6 (5)		0.193
Total cholesterol (under treatment), mg/dL	124.3 ± 26.0	123.4 ± 26.3	125.8 ± 25.5	0.424
Metabolic syndrome, n (%)	204 (62)	124 (60)	80 (68)		0.011
BMI	27.2 ± 4.3	26.9 ± 3.7	27.9 ± 5.2	0.090
AMI characteristics
Anterior, n (%)	171 (52)	138 (66)	33 (28)		< 0.001
Inferior, n (%)	86 (26)	66 (32)	20 (17)		0.003
Other, n (%)	69 (21)	4 (2)	65 (55)		< 0.001
Coronary vessels with critical lesions, n	2.05 ± 0.85	1.94 ± 0.84	2.25 ± 0.85	0.002
1-vessel disease, n (%)	105 (32)	75 (36)	30 (26)		0.014
2-vessels disease, n (%)	97 (30)	68 (33)	29 (25)
3-vessels disease, n (%)	124 (38)	66 (31)	58 (49)
Coronary arteries treated by PCI, n	1.29 ± 0.82	1.34 ± 0.72	1.20 ± 0.97	0.141
Incomplete revascularization, n (%)	151 (46)	87 (42)	64 (54)		0.031
Left ventricle ejection fraction, %	47.2 ± 10.3	47.8 ± 9.2	46.4 ± 12.0	0.222
Patients with LVEF < 40%, n (%)	85 (26)	43 (21)	41 (35)		0.006
Patient with heart failure at initial admission, n (%)	37 (11)	15 (7)	22 (19)		0.002
Time before Holter, d	16.2 ± 9.6	15.6 ± 9.5	17.4 ± 9.8	0.117
Therapy at time of discharge from hospital (number of cases, %)
Aspirin	314 (96)	202 (97)	112 (95)		0.469
Clopidogrel	302 (93)	192 (92)	110 (93)		0.458
Warfarin	38 (12)	22 (11)	16 (14)		0.399
β-blocker	290 (89)	189 (91)	101 (86)		0.198
Ca-antagonist	38 (12)	18 (9)	20 (17)		0.022
ACE-inhibitor	264 (81)	180 (86)	84 (71)		0.001
AT-II-antagonist	43 (13)	16 (8)	27 (23)		< 0.001
Statin	314 (96)	201 (97)	113 (96)		0.893
Diuretic(s)	140 (43)	75 (36)	65 (55)		0.001
HRV parameters
Mean heart rate, bpm	68.1 ± 10.0	69.1 ± 10.1	66.2 ± 9.7	0.016
pNN50	10.1 ± 12.0	9.5 ± 10.5	11.1 ± 14.3	0.245
Triangular Index	18.6 ± 29.9	19.6 ± 44.4	17.0 ± 26.6	0.567
SDNN, ms	105.7 ± 39.1	105.7 ± 39.2	105.7 ± 39.2	0.990
SDNN day, ms	95.8 ± 35.4	95.2 ± 33.9	96.8 ± 37.9	0.688
SDNN night, ms	103.5 ± 41.0	102.8 ± 41.6	104.8 ± 40.1	0.671
RMSSD, ms	45.0 ± 37.7	42.2 ± 30.6	49.9 ± 47.4	0.079
SDANN, ms	92.1 ± 33.1	93.5 ± 35.1	89.7 ± 29.4	0.331
SDNN-i, ms	41.4 ± 22.5	40.7 ± 18.9	42.6 ± 27.7	0.444

¹Level of significance from unpaired t tests for STEMI and NSTEMI patients;

²Level of significance from χ² tests for STEMI and NSTEMI patients. ms: Milliseconds; STEMI: ST-elevation myocardial infarction; NSTEMI: Non-ST-elevation myocardial infarction; CABG: Coronary artery by-pass graft; PCI: Percutaneous coronary intervention; AMI: Acute myocardial infarction; BMI: Body mass index; LVEF: Left ventricle ejection fraction; ACE: Angiotensin converting enzyme; AT-II: Angiotensin II receptor type 2; HRV: Heart rate variability; SDNN: Standard deviation of all normal-to-normal intervals; RMSSD: Root mean square of successive differences between normal-to-normal intervals.