There were no significant differences between the cryo and the RF groups with regard to preoperative, operative, and postoperative characteristics (Table 2). Patients in the No-maze group were older compared with the patients in the intervention groups, but did not differ markedly in other preoperative comorbidities.
Table 2. Pre-, per- and postoperative data of the three study groups
Variables
|
Cryothermia
(n=20)
|
RF
(n=21)
|
p Value* Cryo vs. RF
|
No-maze
(n=19)
|
p Value* No-maze vs. Cryo
|
p Value*
No-maze vs. RF
|
p Value**
|
|
Preoperative data
|
|
|
|
|
|
|
|
|
Female
|
5 (25%)
|
12 (57%)
|
|
7 (37%)
|
|
|
0.11
|
|
Age (years)
|
71 [65-74]
|
72 [66-74]
|
1.0
|
77 [73-78]
|
0.02
|
0.006
|
0.004
|
|
COPD
|
4 (20%)
|
4 (19%)
|
|
2 (10.5%)
|
|
|
0.69
|
|
NYHA III or IV
|
17 (85%)
|
14 (67%)
|
|
15 (79%)
|
|
|
0.37
|
|
Congestive heart failure
|
12 (60%)
|
13 (62%)
|
|
16 (84%)
|
|
|
0.20
|
|
Euroscore II
|
5.1 [3.2-6.7]
|
5.4 [4.3-7.0]
|
|
4.7 [3.2-7.4]
|
|
|
0.88
|
|
Body mass index (kg/m2)
|
25 [24-28]
|
25 [24-29]
|
|
26 [23-29]
|
|
|
0.80
|
|
Non paroxysmal AF
|
15 (75%)
|
15 (71%)
|
|
13 (68%)
|
|
|
0.90
|
|
LVEF <50%
|
5 (26%)
|
6 (29%)
|
|
5 (26%)
|
|
|
0.97
|
|
Left atrium area (cm2)
|
35 [30-40]
|
32 [30-36]
|
|
32 [25-40]
|
|
|
0.35
|
|
TAPSE (mm)
|
19 [17-22]
|
16 [16-21]
|
|
15 [13-20]
|
|
|
0.17
|
|
Right atrium area (cm2)
|
28 [26-31]
|
25 [22-30]
|
|
28 [21-31]
|
|
|
0.29
|
|
Pulmonary artery pressure (mmHg)
|
38 [30-50]
|
43 [32-50]
|
|
50 [35-60]
|
|
|
0.10
|
|
Operative data
|
|
|
|
|
|
|
|
|
Surgery time (min)
|
253 [235-306]
|
253 [225-286]
|
|
220 [195-250]
|
|
|
0.06
|
|
Extracorporeal circulation (min)
|
158 [147-205]
|
163 [148-193]
|
1.00
|
131 [116-178]
|
0.03
|
0.03
|
0.01
|
|
Cross clamp time (min)
|
106 [101-129]
|
95 [86-120]
|
0.31
|
85 [77-100]
|
0.005
|
0.36
|
0.007
|
|
Mitral valve replacement
|
2 (10%)
|
5 (24%)
|
|
5 (26%)
|
|
|
0.39
|
|
Tricuspid valve surgery
|
15 (75%)
|
15 (71%)
|
|
12 (63%)
|
|
|
0.72
|
|
Coronary surgery
|
5 (25%)
|
6 (29%)
|
|
7 (37%)
|
|
|
0.72
|
|
Aortic valve replacement
|
2 (10%)
|
3 (14%)
|
|
2 (11%)
|
|
|
0.90
|
|
Aortic surgery
|
1 (5%)
|
0
|
|
1 (5%)
|
|
|
0.58
|
|
Left atrium appendage resection
|
13 (65%)
|
20 (95%)
|
0.29
|
6 (32%)
|
0.22
|
0.002
|
<0.001
|
|
Inotropic drugs at weaning
|
18 (90%)
|
14 (67%)
|
0.60
|
8 (42%)
|
0.03
|
0.55
|
0.007
|
|
LVAD at weaning
|
1 (5%)
|
0
|
|
0
|
|
|
0.37
|
|
Postoperative outcome
|
|
|
|
|
|
|
|
|
Time on ventilator (h)
|
2.6 [1.8-6.9]
|
4.3 [3.4-11.7]
|
|
7.3 [3.5-10.8]
|
|
|
0.08
|
|
Sinus rhythm at discharge
|
13 (65%)
|
11 (52%)
|
1.00
|
1 (5%)
|
0.004
|
0.03
|
<0.001
|
|
30-day mortality
|
1 (5%)
|
0
|
|
0
|
|
|
0.37
|
|
Stroke, permanent
|
0
|
1 (5%)
|
|
0
|
|
|
0.40
|
|
Dialysis
|
1 (5%)
|
1 (5%)
|
|
2 (11%)
|
|
|
0.72
|
|
Data are presented as the median [25th to 75th percentile] or count (percentage). *Post-hoc comparisons of mean ranks of pairs of groups. **Multiple comparisons of mean ranks for all groups, Kruskal-Wallis test. RF: radio frequency, COPD: chronic obstructive pulmonary disease, NYHA: New York Heart Association class, AF: atrial fibrillation, LVEF: left ventricular ejection fraction, TAPSE: tricuspid annular plane systolic excursion, LVAD: left ventricular assist device.
Table 3. Biochemical markers
Variables
|
Cryothermia
(n=20)
|
RF
(n=21)
|
p Value* Cryo vs. RF
|
No-maze
(n=19)
|
p Value* No-maze vs. Cryo
|
p Value*
No-maze vs. RF
|
p Value**
|
Tn-T (ng/L)
|
|
|
|
|
|
|
|
Preoperative
|
12.5 [8.5-17]
|
12 [9-16]
|
|
15 [11-17]
|
|
|
0.53
|
T0
|
8145 [5095-14440]
|
2140 [1900-3290]
|
0.002
|
709 [517-786]
|
<0.001
|
0.002
|
<0.001
|
T3
|
12805 [6140-15700]
|
2790 [1880-4180]
|
0.002
|
999 [683-1420]
|
<0.001
|
0.002
|
<0.001
|
T20
|
3400 [2785-4900]
|
1980 [1640-2530]
|
0.01
|
798 [565-929]
|
<0.001
|
0.001
|
<0.001
|
Postoperative day 3
|
2095 [1645-3275]
|
1200 [1030-1670]
|
0.005
|
576 [437-754]
|
<0.001
|
0.01
|
<0.001
|
CK-MB (µg/L)
|
|
|
|
|
|
|
|
Preoperative
|
2 [1.5-2.5]
|
2 [1-3]
|
|
2 [2-3]
|
|
|
0.99
|
T0
|
269 [243-352]
|
68 [62-81]
|
<0.001
|
47 [34-59]
|
<0.001
|
0.06
|
<0.001
|
T3
|
271 [217-357]
|
79 [66-93]
|
<0.001
|
48 [32-71]
|
<0.001
|
0.09
|
<0.001
|
T20
|
107 [69-132]
|
53 [42-57]
|
0.005
|
29 [18-43]
|
<0.001
|
0.02
|
<0.001
|
ASAT (µg/L)
|
|
|
|
|
|
|
|
Preoperative
|
0.5 [0.4-0.5]
|
0.5 [0.4-0.5]
|
|
0.5 [0.4-0.6]
|
|
|
0.58
|
T0
T3
T20
|
2.5 [1.8-3.9]
3.3 [2.5-5.9]
3.3 [2.5-3.8]
|
2.4 [1.8-3.4]
2.9 [2-4.1]
2.2 [2-2.6]
|
1.0
0.55
0.006
|
1.2 [0.9-1.5]
1.3 [1.1-1.7]
1.3 [1.0-1.6]
|
<0.001
<0.001
<0.001
|
0.001
<0.001
0.01
|
<0.001
<0.001
<0.001
|
ALAT (µg/L)
|
|
|
|
|
|
|
|
Preoperative
|
0.4 [0.3-0.5]
|
0.4 [0.4-0.5]
|
|
0.4 [0.3-0.5]
|
|
0.64
|
T20
|
0.5 [0.4-0.7]
|
0.5 [0.4-0.6]
|
|
0.5 [0.3-0.6]
|
|
0.16
|
CRP (mg/L)
|
|
|
|
|
|
|
|
Preoperative
|
0.9 [0.4-1.9]
|
1.7 [0.7-3.9]
|
0.40
|
2.8 [1.5-7.2]
|
0.01
|
0.38
|
0.01
|
T20
|
77 [63-86]
|
75 [52-104]
|
|
77 [60-87]
|
|
0.89
|
IL-6 (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
300 [221-510]
|
185 [121-365]
|
|
193 [137-386]
|
|
|
0.23
|
ΔT3-Preoperative
|
223 [159-333]
|
141 [106-279]
|
|
206 [112-317]
|
|
|
0.20
|
ΔT20-Preoperative
|
150 [82-332]
|
120 [85-193]
|
|
222 [135-433]
|
|
|
0.09
|
IL-18 (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
-38 [-65 - -19]
|
-37 [-64 – 6]
|
|
-50 [-60 - -23]
|
|
|
0.87
|
ΔT3-Preoperative
|
-5 [-34 – 9]
|
-38 [-45 - -3]
|
|
-10 [-29 - -3]
|
|
|
0.32
|
ΔT20-Preoperative
|
-11 [-33 - -1]
|
-12 [-34 – 7]
|
|
-28 [-64 - 3]
|
|
|
0.47
|
|
|
|
|
|
|
|
|
STK4 (MST1) (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
-4.0 [-7.1 - -0.1]
|
-2.6 [-12.0 - -1.0]
|
|
-5.0 [-8.6 - -3.1]
|
|
|
0.5
|
ΔT3-Preoperative
|
-3.1 [-5.9 - -0.7]
|
-6.9 [-10.2 - -2.9]
|
|
-5.3 [-7.0 - -1.7]
|
|
|
0.06
|
ΔT20-Preoperative
|
-6.6 [-8.5 - -2.4]
|
-6.1 [-11.2 - -3.1]
|
|
-8.1 [-10.5 - -3.8]
|
|
|
0.6
|
PAR-1 (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
-5.0 [-10.3-17.0]
|
2.2 [-15.6-16.2]
|
|
-7.3 [-18.6-5.6]
|
|
|
0.3
|
ΔT3-Preoperative
|
7.8 [0.1-17.6]
|
-9.8 [-19.3-0.1]
|
0.002
|
-5.0 [-14.6-4.8]
|
0.08
|
0.9
|
0.003
|
ΔT20-Preoperative
|
-8.1 [-18.8-8.0]
|
-17.0 [-21.8-4.0]
|
|
-15.7 [-26.8 - -9.4]
|
|
|
0.3
|
HSP27 (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
259 [98-310]
|
151 [-35-330]
|
0.6
|
106 [-133-174]
|
0.03
|
0.6
|
0.04
|
ΔT3-Preoperative
|
196 [129-278]
|
42 [-181-156]
|
0.02
|
-26 [-115-98]
|
0.001
|
1.0
|
0.007
|
ΔT20-Preoperative
|
-40 [-204-81]
|
-87 [-301-80]
|
|
-138 [-271 - -23]
|
|
|
0.3
|
TRAIL-R2 (NPX)
|
|
|
|
|
|
|
|
ΔT0-Preoperative
|
6.6 [2.7-13.7]
|
8.7 [7.0-21]
|
|
4.2 [2.5-11.3]
|
|
|
0.2
|
ΔT3-Preoperative
|
27 [21-38]
|
23 [17-31]
|
|
20 [17-37]
|
|
|
0.1
|
ΔT20-Preoperative
|
25 [19-33]
|
25 [15-40]
|
|
25 [16-40]
|
|
|
0.9
|
NT-proBNP (ng/L)
|
|
|
|
|
Preoperative
|
1250 [730-1945]
|
1380 [950-1910]
|
|
1620 [1220-3120]
|
|
0.65
|
T20
|
5290 [3295-10615]
|
5470 [3060-9250]
|
|
3730 [2750-5810]
|
|
0.48
|
Postoperative day 3
|
6105 [4300-9185]
|
6000 [3990-11200]
|
|
5430 [3660-14000]
|
|
0.99
|
Data are presented as the median [25th to 75th percentile] or count (%). *Post-hoc comparisons of mean ranks of pairs of groups. **Multiple comparisons of mean ranks for all groups, Kruskal-Wallis test. Cryo: Cryoablation, RF: radio frequency, Tn-T: Troponin T, T0: end of the operation, T3: 3 hours postoperatively, T20: 20 hours postoperatively, CK-MB: Creatine kinase isoenzyme MB, ASAT: aspartate aminotransferase, ALAT: alanine aminotransferase, CRP: C-reactive protein, IL-6: Interleukin-6, NPX: Normalized Protein Expression, IL-18: Interleukin-18, STK4: Serine/threonine-protein Kinase 4, PAR-1: Proteas-activated receptor 1, HSP27: Heat shock protein 27, TRAIL R2: TNF-related apoptosis inducing ligand receptor 2, NT-proBNP: N-terminal pro-B-type natriuretic peptide.
Markers of myocardial injury and their thermal stability
The highest levels of Tn-T, CK-MB, and ASAT were measured 3 h after surgery (Table 3). There were, however, significant differences in Tn-T and CK-MB between all three groups, with the cryo group having the highest levels. There was no significant difference in ASAT between the cryo and the RF groups but both had higher levels than the no-maze group (Fig. 1). Correcting for the patients with only left atrial ablation lines did not influence the median levels of the markers for myocardial injury or the differences between groups. The AF ablation and method explained a large proportion of variance in the peak levels of markers for myocardial injury. Other explanatory variables were CCT, absence of coronary artery disease, and age (Table 4).
We conducted in vitro experiments to evaluate if locally increased temperatures during RF procedures might create a detection bias because of denaturation. To analyze thermal effects on TnT, CK-MB, ASAT, and ALAT detection, plasma samples from 10 patients were heated to 37ºC, 56ºC, 65ºC, and 80ºC for 3 min and the results were compared with a non-heated sample (Fig. 2). Detection of Tn-T and ASAT was unaffected by temperature while ALAT detection was partially affected at 65ºC (Fig. 2). CK-MB levels were temperature dependent and decreased dramatically even at 56ºC, suggesting that the lower levels measured during RF are most probably due to protein denaturation.
Table 4. Multivariable linear regression models to find factors influencing myocardial injury.
Variables
|
Standardized coefficient β
|
95% CI
|
p Value
|
Dependent variable: log10 Tn-T (T3)
Adjusted R² = 0.79
|
|
|
|
Patient groups
(No-maze = 1, RF = 2, Cryo = 3)
|
0.85
|
0.71 to 0.98
|
<0.001
|
Coronary artery disease
(no = 0, yes = 1)
|
-0.18
|
-0.32 to -0.05
|
0.007
|
Age (years)
|
0.15
|
0.02 to 0.28
|
0.02
|
Cross clamp time (min)
|
0.15
|
0.01 to 0.29
|
0.04
|
Dependent variable: log10 CK-MB (T3)
Adjusted R² = 0.70
|
|
|
|
Patient groups
(No-maze = 1, RF = 2, Cryo = 3)
|
0.84
|
0.70 to 0.98
|
<0.001
|
Dependent variable: log10 ASAT (T20)
Adjusted R² = 0.64
|
|
|
|
Patient groups
(No-maze = 1, RF = 2, Cryo = 3)
|
0.66
|
0.49 to 0.83
|
<0.001
|
Cross clamp time (min)
|
0.26
|
0.08 to 0.44
|
0.005
|
Coronary artery disease
(no = 0, yes = 1)
|
-0.20
|
-0.37 to -0.03
|
0.02
|
Multivariable linear regression models showing the factors with significant influence on myocardial injury. The Tn-T and CK-MB at 3 h postoperatively and ASAT at 20 h postoperatively were chosen as dependent factors and log10 transformed to align with the assumption of Gaussian distribution. The models were fit by an enter method. The extent of ablation was excluded from the models due to multicollinearity with the study groups. 95%CI: 95% confidence interval, RF: radio frequency, Tn-T: troponin T, CK-MB: creatine kinase isoenzyme MB, ASAT: aspartate aminotransferase, T3: 3 hours postoperatively, T20: 20 hours postoperatively.
Markers of inflammation (CRP, IL-6, and IL-18)
There were no significant differences in postoperative CRP levels between the three groups (Table 2). Both preoperative CRP and CCT correlated with CRP 20 h postoperatively (rs = 0.41, P = 0.001 and rs = 0.22, P = 0.01, respectively) in the whole study population. No significant differences between the three groups of patients regarding the pro-inflammatory cytokines IL-6 and IL-18 were found at any time point (Table 3).
Markers of cell stress and apoptosis (PAR-1, HSP27, STK4, TRAIL R2)
PAR-1 elevation from preoperation to 3 hours after surgery (ΔT3) was significantly higher in the cryo compared with the RF group (P = 0.002) (Table 3, Fig. 3). ΔT3 HSP27 levels also differed significantly between the three study groups (P = 0.007) and in pairwise comparison, increased levels were found in the cryo compared with the RF group (P = 0.002) and compared with the no-maze group (P = 0.001), but there was no difference between RF and No-maze patients (Table 3, Fig. 4). At ΔT3, the decrease in STK4 had a tendency to be more pronounced in the RF group compared with the cryo group, although not statistically significant (P = 0.06). TRAIL-R2 did not show any significant differences between the study groups.
Marker of heart failure (NT-proBNP)
There were no significant differences in postoperative NT-proBNP levels between the three groups (Table 3). Preoperative NT-proBNP correlated with NT-proBNP at 20 h and 3 days postoperatively (rs = 0.48, P < 0.001 and rs = 0.58, P < 0.001, respectively) but there were no significant correlations between CCT and postoperative NT-proBNP levels (rs = 0.11, P = 0.4 and rs = -0.14, P = 0.3, respectively).