Cardiol Res

Cardiology Research, ISSN 1923-2829 print, 1923-2837 online, Open Access

Article copyright, the authors; Journal compilation copyright, Cardiol Res and Elmer Press Inc

Journal website https://cr.elmerpub.com

Original Article

Volume 17, Number 3, June 2026, pages 205-213

Comparison of Single-Freezing Temperature-Guided and Conventional Time-to-Isolation-Guided Protocols of Cryoballoon in Atrial Fibrillation Ablation

↓ Figure 1. Kaplan–Meier survival analysis of patients with sinus rhythm maintenance after procedure in the conventional time-to-isolation-guided protocol (conventional group) and single-freezing temperature-guided protocol (simplified group).

↓ Figure 2. X-ray image of the relative position between the Achieve electrode (black arrow) and the cryoballoon (white arrow) during the cryoablation process. (a) The cryoballoon and Achieve electrode are both located near the pulmonary vein vestibule. (b) The cryoballoon is placed near the pulmonary vein vestibule, and the Achieve electrode penetrates deep into the pulmonary vein.

↓ **Table 1.** Comparison of the Overall Procedural Parameters of Two Groups
	Conventional group (n = 153)	Simplified group (n = 318)	P value	PSM conventional group (n = 146)	PSM simplified group (n = 146)	P value
AF: atrial fibrillation; BMI: body mass index; CHD: coronary atherosclerotic heart disease; LA: left atrial; LVEF: left ventricular ejection fraction; PSM: propensity score matching; TIA: transient ischemic attack.
Gender (male/female)	92/61	190/128	0.937	87/59	86/60	0.905
Age (years)	61.1 ± 11.1	61.8 ± 9.8	0.480	61.1 ± 11.3	60.8 ± 10.2	0.778
Height (cm)	167.1 ± 8.4	167.4 ± 8.3	0.761	167.1 ± 8.3	166.5 ± 8.0	0.576
Weight (kg)	69.5 ± 10.7	70.8 ± 11.1	0.234	69.7 ± 10.7	69.3 ± 11.0	0.732
BMI (kg/m²)	24.8 ± 2.9	25.2 ± 3.1	0.190	24.9 ± 2.9	24.9 ± 3.1	0.975
Course of AF (months)	48.7 ± 69.9	47.6 ± 56.4	0.190	49.7 ± 71.1	50.1 ± 63.5	0.382
Paroxysmal AF	94 (61.4%)	189 (59.4%)	0.677	89 (61.0%)	85 (58.2%)	0.633
Basic diseases
Hypertension	86 (56.2%)	201 (63.2%)	0.145	85 (58.2%)	84 (57.5%)	0.905
CHD	19 (12.4%)	38 (11.9%)	0.884	19 (13.0%)	17 (11.6%)	0.722
Diabetes	20 (13.1%)	57 (17.9%)	0.182	20 (13.7%)	18 (12.3%)	0.728
Stock/TIA	12 (7.8%)	33 (10.4%)	0.381	12 (8.2%)	12 (8.2%)	1.000
Heart failure	5 (3.3%)	4 (1.3%)	0.136	1 (0.7%)	2 (1.4%)	1.000
LA diameter (mm)	40.9 ± 5.6	40.6 ± 5.8	0.627	40.7 ± 5.5	40.4 ± 6.2	0.734
LVEF (%)	62.5 ± 3.6	62.9 ± 3.9	0.291	62.6 ± 3.6	62.9 ± 4.2	0.502
CHA₂DS₂-VASc	1.4 ± 1.0	1.5 ± 1.1	0.254	1.4 ± 1.0	1.4 ± 1.1	0.801
Antiarrhythmic drugs
β-blocker	139 (90.8%)	300 (94.3%)	0.159	134 (91.8%)	140 (95.9%)	0.144
Amiodarone	127 (83.0%)	255 (80.2%)	0.464	123 (84.2%)	117 (80.1%)	0.359
Propafenone	17 (11.1%)	36 (11.3%)	0.946	15 (10.3%)	16 (11.0%)	0.849

↓ Table 1. Comparison of the Overall Procedural Parameters of Two Groups

Conventional group (n = 153)

Simplified group (n = 318)

P value

PSM conventional group (n = 146)

PSM simplified group (n = 146)

P value

AF: atrial fibrillation; BMI: body mass index; CHD: coronary atherosclerotic heart disease; LA: left atrial; LVEF: left ventricular ejection fraction; PSM: propensity score matching; TIA: transient ischemic attack.

Gender (male/female)

92/61

190/128

0.937

87/59

86/60

0.905

Age (years)

61.1 ± 11.1

61.8 ± 9.8

0.480

61.1 ± 11.3

60.8 ± 10.2

0.778

Height (cm)

167.1 ± 8.4

167.4 ± 8.3

0.761

167.1 ± 8.3

166.5 ± 8.0

0.576

Weight (kg)

69.5 ± 10.7

70.8 ± 11.1

0.234

69.7 ± 10.7

69.3 ± 11.0

0.732

BMI (kg/m²)

24.8 ± 2.9

25.2 ± 3.1

0.190

24.9 ± 2.9

24.9 ± 3.1

0.975

Course of AF (months)

48.7 ± 69.9

47.6 ± 56.4

0.190

49.7 ± 71.1

50.1 ± 63.5

0.382

Paroxysmal AF

94 (61.4%)

189 (59.4%)

0.677

89 (61.0%)

85 (58.2%)

0.633

Basic diseases

Hypertension

86 (56.2%)

201 (63.2%)

0.145

85 (58.2%)

84 (57.5%)

0.905

CHD

19 (12.4%)

38 (11.9%)

0.884

19 (13.0%)

17 (11.6%)

0.722

Diabetes

20 (13.1%)

57 (17.9%)

0.182

20 (13.7%)

18 (12.3%)

0.728

Stock/TIA

12 (7.8%)

33 (10.4%)

0.381

12 (8.2%)

1.000

Heart failure

5 (3.3%)

4 (1.3%)

0.136

1 (0.7%)

2 (1.4%)

1.000

LA diameter (mm)

40.9 ± 5.6

40.6 ± 5.8

0.627

40.7 ± 5.5

40.4 ± 6.2

0.734

LVEF (%)

62.5 ± 3.6

62.9 ± 3.9

0.291

62.6 ± 3.6

62.9 ± 4.2

0.502

CHA₂DS₂-VASc

1.4 ± 1.0

1.5 ± 1.1

0.254

1.4 ± 1.0

1.4 ± 1.1

0.801

Antiarrhythmic drugs

β-blocker

139 (90.8%)

300 (94.3%)

0.159

134 (91.8%)

140 (95.9%)

0.144

Amiodarone

127 (83.0%)

255 (80.2%)

0.464

123 (84.2%)

117 (80.1%)

0.359

Propafenone

17 (11.1%)

36 (11.3%)

0.946

15 (10.3%)

16 (11.0%)

0.849

↓ **Table 2.** Procedural Parameters
	PSM conventional group (n = 146)	PSM simplified group (n = 146)	P value
LCPV: left common pulmonary vein; LIPV: left inferior pulmonary vein; LSPV: left superior pulmonary vein; PSM: propensity score matching; PV: pulmonary vein; RIPV: right superior pulmonary vein; RMPV: right middle pulmonary vein; RSPV: right inferior pulmonary vein.
Procedure time (min)	98.7 ± 15.8	82.3 ± 12.5	< 0.001
Routine procedure time (min)	36.8 ± 5.4	37.9 ± 6.5	0.125
Freezing procedure time (min)	61.8 ± 16.4	44.4 ± 12.9	< 0.001
Total X-ray time (min)	24.2 ± 6.8	18.8 ± 5.4	< 0.001
Routine procedure X-ray time (min)	7.7 ± 2.0	7.7 ± 1.9	0.854
Freezing procedure X-ray time (min)	16.5 ± 6.3	11.1 ± 5.2	< 0.001
Total X-ray dose (mGy)	676.4 ± 333.0	539.6 ± 387.3	< 0.001
Routine procedure X-ray dose (mGy)	160.4 ± 70.6	177.9 ± 84.3	0.098
Freezing procedure X-ray dose (mGy)	516.0 ± 281.3	361.7 ± 341.7	< 0.001
PV variant	26 (17.8%)	27 (18.5%)	0.879
Total freeze applications	9.3 ± 1.6	4.9 ± 1.3	< 0.001
Total freeze duration (s)	1,279.1 ± 158.7	824.4 ± 116.1	< 0.001
LSPV	130 (89.0%)	129 (88.4%)	0.853
LSPV freeze applications	2.2 ± 0.5	1.2 ± 0.5	< 0.001
LSPV freeze duration (s)	311.5 ± 27.8	199.0 ± 34.1	< 0.001
LSPV nadir temperature (°C)	−50.8 ± 4.4	−50.0 ± 5.1	0.166
LIPV	130 (89.0%)	129 (88.4%)	0.853
LIPV freeze applications	2.3 ± 0.6	1.2 ± 0.5	< 0.001
LIPV freeze duration (s)	316.9 ± 39.1	203.6 ± 45.7	< 0.001
LIPV nadir temperature (°C)	−49.1 ± 5.5	−49.2 ± 5.8	0.615
RSPV	146 (100%)	146 (100%)	-
RSPV freeze applications	2.2 ± 0.6	1.3 ± 0.5	< 0.001
RSPV freeze duration (s)	315.3 ± 42.4	215.0 ± 51.3	< 0.001
RSPV nadir temperature (°C)	−49.5 ± 5.8	−48.9 ± 6.5	0.393
RIPV	146 (100%)	146 (100%)	-
RIPV freeze applications	2.6 ± 0.8	1.2 ± 0.6	< 0.001
RIPV freeze duration (s)	341.4 ± 56.9	211.1 ± 47.5	< 0.001
RIPV nadir temperature (°C)	−43.9 ± 6.3	−44.9 ± 5.9	0.110
LCPV	16 (11.0%)	17 (11.6%)	0.853
LCPV freeze applications	2.8 ± 0.9	1.8 ± 1.1	0.007
LCPV freeze duration (s)	363.8 ± 86.2	285.9 ± 107.2	0.009
LCPV nadir temperature (°C)	−41.3 ± 4.4	−38.3 ± 4.8	0.071
RMPV	10 (6.8%)	10 (6.8%)	1.000
RMPV freeze applications	2.4 ± 0.5	1.2 ± 0.4	< 0.001
RMPV freeze duration (s)	336.0 ± 26.3	210.0 ± 42.4	< 0.001
RMPV nadir temperature (°C)	−46.9 ± 4.1	−45.9 ± 5.6	0.319

↓ Table 2. Procedural Parameters

PSM conventional group (n = 146)

PSM simplified group (n = 146)

P value

LCPV: left common pulmonary vein; LIPV: left inferior pulmonary vein; LSPV: left superior pulmonary vein; PSM: propensity score matching; PV: pulmonary vein; RIPV: right superior pulmonary vein; RMPV: right middle pulmonary vein; RSPV: right inferior pulmonary vein.

Procedure time (min)

98.7 ± 15.8

82.3 ± 12.5

< 0.001

Routine procedure time (min)

36.8 ± 5.4

37.9 ± 6.5

0.125

Freezing procedure time (min)

61.8 ± 16.4

44.4 ± 12.9

< 0.001

Total X-ray time (min)

24.2 ± 6.8

18.8 ± 5.4

< 0.001

Routine procedure X-ray time (min)

7.7 ± 2.0

7.7 ± 1.9

0.854

Freezing procedure X-ray time (min)

16.5 ± 6.3

11.1 ± 5.2

< 0.001

Total X-ray dose (mGy)

676.4 ± 333.0

539.6 ± 387.3

< 0.001

Routine procedure X-ray dose (mGy)

160.4 ± 70.6

177.9 ± 84.3

0.098

Freezing procedure X-ray dose (mGy)

516.0 ± 281.3

361.7 ± 341.7

< 0.001

PV variant

26 (17.8%)

27 (18.5%)

0.879

Total freeze applications

9.3 ± 1.6

4.9 ± 1.3

< 0.001

Total freeze duration (s)

1,279.1 ± 158.7

824.4 ± 116.1

< 0.001

LSPV

130 (89.0%)

129 (88.4%)

0.853

LSPV freeze applications

2.2 ± 0.5

1.2 ± 0.5

< 0.001

LSPV freeze duration (s)

311.5 ± 27.8

199.0 ± 34.1

< 0.001

LSPV nadir temperature (°C)

−50.8 ± 4.4

−50.0 ± 5.1

0.166

LIPV

130 (89.0%)

129 (88.4%)

0.853

LIPV freeze applications

2.3 ± 0.6

1.2 ± 0.5

< 0.001

LIPV freeze duration (s)

316.9 ± 39.1

203.6 ± 45.7

< 0.001

LIPV nadir temperature (°C)

−49.1 ± 5.5

−49.2 ± 5.8

0.615

RSPV

146 (100%)

RSPV freeze applications

2.2 ± 0.6

1.3 ± 0.5

< 0.001

RSPV freeze duration (s)

315.3 ± 42.4

215.0 ± 51.3

< 0.001

RSPV nadir temperature (°C)

−49.5 ± 5.8

−48.9 ± 6.5

0.393

RIPV

146 (100%)

RIPV freeze applications

2.6 ± 0.8

1.2 ± 0.6

< 0.001

RIPV freeze duration (s)

341.4 ± 56.9

211.1 ± 47.5

< 0.001

RIPV nadir temperature (°C)

−43.9 ± 6.3

−44.9 ± 5.9

0.110

LCPV

16 (11.0%)

17 (11.6%)

0.853

LCPV freeze applications

2.8 ± 0.9

1.8 ± 1.1

0.007

LCPV freeze duration (s)

363.8 ± 86.2

285.9 ± 107.2

0.009

LCPV nadir temperature (°C)

−41.3 ± 4.4

−38.3 ± 4.8

0.071

RMPV

10 (6.8%)

1.000

RMPV freeze applications

2.4 ± 0.5

1.2 ± 0.4

< 0.001

RMPV freeze duration (s)

336.0 ± 26.3

210.0 ± 42.4

< 0.001

RMPV nadir temperature (°C)

−46.9 ± 4.1

−45.9 ± 5.6

0.319

↓ **Table 3.** Outcomes of Procedure
	PSM conventional group (n = 146)	PSM simplified group (n = 146)	P value
Success of first anatomical attempt is defined as the absence of PV potentials after the first ablation circle, and no recovery of potentials is observed during the check. Acute success was defined as achievement of entrance block confirmed after the final freeze application, with no potentials recorded in any PV at the end of the procedure. PSM: propensity score matching.
Success of first anatomical attempt	143 (97.9%)	132 (90.4%)	0.022
Acute success	145 (99.3%)	146 (100%)	0.975
Complications (major)	1 (0.7%)	1 (0.7%)	0.596
Complications (minor)	3 (2.1%)	7 (4.8%)	0.772
Follow-up (months)	11.2 ± 3.6	11.8 ± 3.8	0.329
Maintenance of sinus rhythm	114 (78.1%)	109 (74.7%)	0.842

↓ Table 3. Outcomes of Procedure

PSM conventional group (n = 146)

PSM simplified group (n = 146)

P value

Success of first anatomical attempt is defined as the absence of PV potentials after the first ablation circle, and no recovery of potentials is observed during the check. Acute success was defined as achievement of entrance block confirmed after the final freeze application, with no potentials recorded in any PV at the end of the procedure. PSM: propensity score matching.

Success of first anatomical attempt

143 (97.9%)

132 (90.4%)

0.022

Acute success

145 (99.3%)

146 (100%)

0.975

Complications (major)

1 (0.7%)

0.596

Complications (minor)

3 (2.1%)

7 (4.8%)

0.772

Follow-up (months)

11.2 ± 3.6

11.8 ± 3.8

0.329

Maintenance of sinus rhythm

114 (78.1%)

109 (74.7%)

0.842

↓ **Table 4.** Analysis With Cox Regression in the Propensity Score-Matched Cohort
Variables	Univariate analysis	Multivariate analysis
AF: atrial fibrillation; BMI: body mass index; CHD: coronary atherosclerotic heart disease; CI: confidence interval; HR: hazard ratio; LA: left atrial; TIA: transient ischemic attack.
Sex
Female	1.000
Male	0.865	0.532–1.408	0.560
Age (years)	1.020	0.996–1.044	0.104	1.016	0.991–1.043	0.216
BMI (kg/m²)	1.011	0.934–1.095	0.781
Course of AF (months)	1.002	0.999–1.005	0.232
Classification of AF
Paroxysmal	1.000
Non-paroxysmal	2.243	1.390–3.619	0.001	1.859	1.057–3.271	0.031
CHA₂DS₂-VASc	1.082	0.875–1.337	0.469
Basic diseases
Hypertension	1.514	0.918–2.498	0.104	1.380	0.832–2.289	0.212
CHD	0.776	0.355–1.695	0.524
Diabetes	1.135	0.581–2.219	0.710
Stroke/TIA	1.243	0.569–2.716	0.585
Heart failure	1.533	0.213–11.045	0.671
LA diameter (mm)	1.066	1.025–1.108	0.001	1.032	0.983–1.084	0.203
Modality
Conventional	1.000
Simplified	1.150	0.716–1.846	0.564

↓ Table 4. Analysis With Cox Regression in the Propensity Score-Matched Cohort

Variables

Univariate analysis

Multivariate analysis

95.0% CI

P value

95.0% CI

P value

AF: atrial fibrillation; BMI: body mass index; CHD: coronary atherosclerotic heart disease; CI: confidence interval; HR: hazard ratio; LA: left atrial; TIA: transient ischemic attack.

Sex

Female

1.000

Male

0.865

0.532–1.408

0.560

Age (years)

1.020

0.996–1.044

0.104

1.016

0.991–1.043

0.216

BMI (kg/m²)

1.011

0.934–1.095

0.781

Course of AF (months)

1.002

0.999–1.005

0.232

Classification of AF

Paroxysmal

1.000

Non-paroxysmal

2.243

1.390–3.619

0.001

1.859

1.057–3.271

0.031

CHA₂DS₂-VASc

1.082

0.875–1.337

0.469

Basic diseases

Hypertension

1.514

0.918–2.498

0.104

1.380

0.832–2.289

0.212

CHD

0.776

0.355–1.695

0.524

Diabetes

1.135

0.581–2.219

0.710

Stroke/TIA

1.243

0.569–2.716

0.585

Heart failure

1.533

0.213–11.045

0.671

LA diameter (mm)

1.066

1.025–1.108

0.001

1.032

0.983–1.084

0.203

Modality

Conventional

1.000

Simplified

1.150

0.716–1.846

0.564