TactiCath Quartz catheter for percutaneous radiofrequency ablation in atrial fibrillation

Study component

Description

Objectives/hypotheses

To determine the safety and effectiveness of TactiCath in the treatment of patients with paroxysmal atrial fibrillation (AF).

Study design

TOCCASTAR study. Randomised controlled trial.

Patients randomised in 1:1 ratio to a contact force sensing catheter (TactiCath^a, intervention) or standard catheter without contact force sensing technology (ThermoCool, control).

Different navigation systems were used in each arm: EnSite NavX with TactiCath, CARTO with ThermoCool.

3 month blanking period included after initial procedure, with a maximum of 2 repeated ablation procedures allowed with the initial catheter type assigned.

Setting

Multicentre – 17 study centres (USA, Czech Republic, France, Switzerland)^b. Dates of enrolment and follow‑up not reported.

Inclusion/exclusion criteria

Inclusion criteria: patients with symptomatic, paroxysmal AF refractory or intolerant to at least 1 class I to IV antiarrhythmic drug (AAD), planned for catheter ablation, at least 1 documented episode of AF >30 seconds, minimum of 3 episodes documented by history within 12 months before enrolment.

Exclusion criteria: persistent AF, myocardial infarction within 3 months prior to intervention, prior left atrial ablation (surgical or catheter), left atrial diameter >5 cm, left ventricular ejection fraction <35%, contraindications to long‑term antithrombotic therapy, severe pulmonary disease.

Primary outcomes

Short‑term ablation success defined as complete isolation of all pulmonary veins (PVs) at the end of the initial procedure.

Long‑term ablation success defined as freedom from recurrence of symptomatic AF, atrial tachycardia or atrial flutter at 12 months after the initial procedure and off AADs, with the exclusion of 3‑month blanking period. Any acute procedural failure, retreatment with ablation, use of class I or III AAD or symptomatic recurrence documented by transtelephonic monitoring (TTM) or electrocardiogram (ECG) after the blanking period constituted treatment failure. Additional outcome of clinically relevant success required AAD use after blanking period to be associated with documentation of arrhythmia through TTM (with at least 3 positive TTMs) or ECG.

Secondary outcomes: device‑related serious adverse events occurring within 7 days of the initial procedure or hospital discharge (whichever was later). Events were classified as primarily device‑ or procedure‑related and adjudicated by an independent clinical events committee. Subgroup analysis of intervention cohort; optimal contact force (CF) group with ≥90% of lesions created with CF ≥10 g, and non‑optimal CF group with patients with <90% of lesions created with CF ≥10 g.

Statistical methods

Study powered to evaluate the non‑inferiority of intervention compared to control catheter. Power calculation assumed treatment success rate of 55% in both groups, 80% power, non‑inferiority margin of 9% for safety and 15% for effectiveness, one‑sided 5% significance level, and 10% attrition.

Categorical variables compared with Fisher's exact test. Continuous variables compared with Mann‑Whitney U test. One‑sided tests used in comparisons involving the optimal CF group, 2‑sided tests used otherwise. A p value <0.05 was considered to be statistically significant. Logistic regression analysis for treatment success was conducted to investigate potential treatment differences across study centres.

Patients included

Total of 317 patients enrolled; 17 were considered roll‑in patients to allow for initial familiarisation with the TactiCath device, and the ablation catheters were not introduced in 5 patients. The 295 remaining patients were included in safety analysis (TactiCath intervention group n=152, control group n=143).

A further 15 patients were excluded from effectiveness analysis; PVI was not attempted in 5 patients and in 10 there was a major deviation from protocol. The 280 remaining patients were included in the effectiveness analysis (TactiCath intervention group n=146, control group n=134).

Results

Short‑term ablation success was achieved in 100% of the patients in both groups. Long‑term ablation success (at 12 months) achieved in 67.8% and 69.4% of the intervention and control groups respectively (p=0.0073). Long‑term clinically relevant success achieved in 78.1% and 80.6% of the intervention and control groups respectively (p=0.659). In the intervention group long‑term success was achieved in 75.9% and 58.1% of the optimal CF and non‑optimal CF subgroups (p=0.018).

Device‑related serious adverse events occurred in 1.97% and 1.40% of intervention and control groups respectively (p=0.0004).

Conclusions

CF ablation catheter met the primary safety and effectiveness endpoints. Additionally, optimal CF was associated with improved effectiveness.

Abbreviations: AAD, antiarrhythmic drug; AF, atrial fibrillation; CF, contact force; ECG, electrocardiogram; g, grams; n, number of patients; PV, pulmonary vein; PVI, pulmonary vein isolation; TTM, transtelephonic monitoring.

^a The manufacturer has informed NICE that this study used TactiCath Quartz, although this is not stated in the paper.

^b Not explicitly stated but assumed from author affiliations.

Intervention:

Catheter ablation with contact force (TactiCath)

Control:

Catheter ablation without contact force (ThermoCool)

Analysis

Randomised

n=155

n=145

Efficacy

n=146

n=134

Primary outcome: short‑term ablation success (initial procedure)

30 min waiting time PV reconnection rate: 10.4%

Final PV isolation rate: 100%

30 min waiting time PV reconnection rate: 13.8%

Final PV isolation rate: 100%

p=0.206

Selected secondary outcomes:

Repeat ablation procedures

During blanking period: n=6

After blanking period: n=16

During blanking period: n=6

After blanking period: n=17 (including 1 subject who required a third procedure)

Long‑term ablation success

(12 months)

67.8%

69.4%

Absolute difference: −1.6%

Lower 95% confidence interval: −10.7% (which is within the predefined 15% non‑inferiority margin)

p=0.0073 for non‑inferiority

Long‑term clinically relevant success

(12 months)

78.1%

(85.5% in the optimal CF subgroup and 67.7% in the non‑optimal CF subgroup, p=0.009)

80.6%

p=0.659

Quality of life

Significant changes were observed in both groups with a non‑significant trend for the intervention versus control group.

Safety

n=152

n=143

Procedure time, median

Fluoroscopy: 27.0 min

Fluoroscopy: 23.0 min

p=0.044

Radiofrequency ablation: 46.5 min

Radiofrequency ablation: 53.0 min

p=0.018

Serious adverse events

Overall: 7.2% (11/152)

Device related: 1.97% (3/152)

Overall: 9.09% (13/143)

Device related: 1.40% (2/143)

Absolute difference: 0.57%

Upper 1‑sided 95% CI: 3.61% (which is within the predefined 9% non‑inferiority margin)

p=0.0004 for non‑inferiority

Abbreviations: CI, confidence interval; min, minutes; n, number of patients; PV, pulmonary vein.

Study component

Description

Objectives/hypotheses

To compare procedural parameters and clinical outcomes between pulmonary vein isolation (PVI) ablation procedures conducted using a contact force‑sensing catheter (TactiCath) and a standard ablation catheter.

Study design

Prospective non‑randomised interventional study.

The first 35 patients were included in the standard ablation catheter group, the subsequent 32 patients were included in the TactiCath group.

Setting

Single‑centre (Germany). Consecutive patients enrolled (dates of enrolment and follow‑up not reported).

Inclusion/exclusion criteria

Inclusion criteria: patients with AF undergoing circumferential PVI for all pulmonary veins.

Exclusion criteria: circumferential isolation of all pulmonary veins with additional ablation lines or complex fractionated atrial electrogram ablation.

Primary outcomes

Freedom from AF at 6‑ and 12‑month follow‑up. Recurrence of AF was defined as at least 1 episode >30 s documented either in baseline ECG or Holter ECG recordings, or clear AF‑related symptoms (palpitations or tachyarrhythmias), or atypical atrial flutter or atrial tachycardia reported after a blanking period of 12 weeks after PVI.

Secondary outcomes: left atrial procedure time (time from first to last ablation to achieve complete isolation), number of energy applications needed to achieve isolation, total fluoroscopy time, absolute decrease in impedance during first 10 s of every energy application (serving as a potential index of lesion efficiency).

Statistical methods

Unpaired Student's t‑test used for 2‑group comparisons. One‑way ANOVA with post‑hoc Bonferroni correction used for multivariate analysis. Calculation of correlation performed using Pearson correlation coefficient. p‑values <0.05 considered statistically significant.

Patients included

Total of n=67 consecutive patients underwent PVI

n=32 underwent catheter ablation with TactiCath (with contact force), n=35 underwent ablation using a standard catheter, ThermoCool (without contact force).

An additional decapolar catheter was used in the coronary sinus for reference and a lasso catheter for anatomical mapping for each patient.

Results

Freedom of AF similar between the groups: 62.5 vs. 62.9% after 6 months, 59.4 vs. 62.9% after 12 months for the TactiCath and standard ablation catheter groups, respectively.

A significant reduction in left atrial procedural time (78.08 vs. 92.52 min, p<0.05) and fluoroscopy time (33.0 vs. 51.4 min, p<0.0001) was found in the TactiCath group.

Conclusions

Use of contact force‑sensing catheters in PVI has a beneficial effect on procedural parameters.

Abbreviations: AF, atrial fibrillation; ANOVA, analysis of variance; ECG, electrocardiogram; min, minutes; n, number of patients; PVI, pulmonary vein isolation; s, seconds.

Catheter ablation with contact force (TactiCath)

Standard ablation catheter (ThermoCool)

Analysis

Randomised

Not applicable

Not applicable

Efficacy

n=32

n=35

Primary outcome: freedom from AF

62.5% at 6 months

62.9% at 6 months

p=0.864

59.4% at 12 months

62.9% at 12 months

p=0.780

Increased freedom from AF after 12 months in paroxysmal AF patients: 73.7 vs. 48.1% for paroxysmal and persistent AF patients respectively, p<0.05]

Paroxysmal AF at 12 months: 72.2%

Paroxysmal AF at 12 months: 71.4%

p=0.734

Persistent AF at 12 months: 50.0%

Persistent AF at 12 months: 42.9%

p=0.585

Selected secondary outcomes:

Impedance reduction in first 10 s (Ω; mean±SD)

9.09±0.53 

6.58±0.33 

p<0.001

Number of energy applications required to isolate pulmonary vein

34.06±3.11

44.20±3.67

p<0.05

Safety

n=32

n=35

Procedure times

(min^a; mean±SD)

Left atrial procedure: 78.08±7.23 

Left atrial procedure: 95.52±7.35

p=0<0.05

Fluoroscopy: 33.0±2.7 

Fluoroscopy: 51.4±3.3 

p<0.001

Force per energy application

(mean±SD)

Contact force: 17.4±1.04 g

Force‑time integral: 713.35±44.64 gs

Not applicable

Complications

Severe complications: None

Total complication rate: 6.3%

Severe complications: None

Total complication rate: 5.7%

Two patients (1 patient in each group) showed small pericardial effusion without indication for pericardiocentesis and 2 patients (1 patient in each group) showed femoral arteriovenous fistula or aneurysm with indication for intervention.

Abbreviations: AF, atrial fibrillation; g, grams; gs, gram‑seconds; min, minutes; n, number of patients; s, seconds; SD, standard deviation.

^a Units not explicitly reported but assumed to be minutes.

Study component

Description

Objectives/hypotheses

To evaluate the impact of catheter contact force monitoring during pulmonary vein isolation (PVI) on AF recurrence rate.

Study design

Non‑randomised comparator study using data from a local prospective AF ablation registry.

Setting

Single‑centre (Germany).

Consecutive patients enrolled between 2010 and 2012.

Inclusion/exclusion criteria

Inclusion criteria: patients with drug refractory symptomatic AF. Procedures conducted by physicians with at least 4 years' experience in interventional electrophysiology, performing >100 PVI procedures a year.

Exclusion criteria: repeat procedures, cases where alternative ablation strategies (linear lesions, ablation of complex fractionated atrial electrograms) or alternative techniques (cryoblation, 'single‑shot' devices, robotic ablation), patients with left ventricular ejection fraction <45%, post‑surgical valve replacement.

Primary outcomes

Recurrence of AF within 12 months.

Secondary outcomes: Ablation time, total procedure time, total ablation energy, fluoroscopy time, procedural complications, total number and reason for non‑scheduled healthcare visits at 12‑month follow‑up and additional medications prescribed during 12‑month follow‑up.

Statistical methods

Categorical data analysed using the Chi² test. Continuous variables analysed using the 2‑sample t‑test for normally distributed data, and the Wilcoxon rank sum test for skewed data. A p‑value of <0.05 considered to be statistically significant.

Patients included

143 patients underwent catheter ablation for symptomatic drug refractory AF.

n=31 underwent catheter ablation with contact force (TactiCath group), n=112 underwent catheter mapping and ablation without the use of contact force using CoolPath, St Jude Medical catheters (control group)^a.

Results

AF recurrence occurred in 36.6% (41/112) of patients in the control group and in 16.1% (5/31) of patients in the TactiCath group (p=0.031).

As significant reduction in total procedure duration was seen in the TactiCath group (128.4±29 min vs. 157.7±30.8 min, p=0.001).

Conclusions

PVI conducted with the use of contact force information results in shorter procedure duration and a lower rate of AF recurrence after 12 months compared with conventional PVI without this information.

Abbreviations: AF, atrial fibrillation; min, minutes; n, number of patients; PVI, pulmonary vein isolation.

^a 19 (61.3%) of the TactiCath group and 85 (75.9%) of the control group had paroxysmal AF. Diagnosis of the remaining patients is not reported.

Catheter ablation with contact force (TactiCath)

Catheter ablation without contact force (CoolPath)

Analysis

Randomised

Not applicable

Not applicable

Efficacy

n=31

n=112

Primary outcome: atrial fibrillation recurrence at 12 months

16.1% (5/31)

36.6% (41/112)

p=0.031

Selected secondary outcomes:

Complete PVI verified by bidirectional block (at procedure)

100% (31/31)

100% (112/112)

Contact force (g; mean±SD)

26.8±10.7

Not applicable

Force‑time integral (gs; mean±SD)

1449.4±415 

Not applicable

Safety

n=31

n=112

Procedure time

(min; mean±SD)

Ablation: 38.6±12.7

Ablation: 45.2±16.5

p=0.13

Total procedure: 128.4±29.0

Total procedure: 157.7±30.8

p=0.001

Fluoroscopy: 39.7±11.3 

Fluoroscopy: 43.8±14.5 

p=0.5

Total energy delivered: (Ws, mean±SD)

71964.4±17894.8 

78579.3±45534

p=0.9

Major complications

None

1 pericardial effusion (0.9%)

Minor complications

1 femoral haematoma (3.2%)

No steam pops were reported

3 femoral haematoma (2.7%)

No steam pops were reported

p=0.75

Unscheduled visits^a

9.7% (3/31)

17.9% (20/112)

p=0.27

Abbreviations: g, grams; gs, gram‑seconds; min, minutes, n, number of patients; PVI, pulmonary vein isolation; s, second; SD, standard deviation; Ws, watt‑seconds.

^a Assumed unscheduled outpatient visits but not explicitly stated.

A novel radiofrequency ablation catheter using contact force sensing: TOCCATA study (Kuck et al. 2012)

Design

TOCCATA study. Prospective, single‑arm, multicentre interventional study.

The purpose was to evaluate the device‑ and procedure‑related safety of the TactiCath force‑sensing catheter during percutaneous ablation for the treatment of cardiac arrhythmias. Two study groups including confirmed paroxysmal atrial fibrillation cohort.

Only results of the paroxysmal atrial fibrillation group will be reported in this summary table, n=34.

Efficacy

Variable number of patients

Primary outcome:

contact force during ablation

During mapping, significant differences in the forces applied in the left atrium were observed between the 12 investigators (p<0.0001), with mean values ranging from 12 to 39 g.

During ablation, a high variability was seen in the forces applied both between investigators (p<0.0001) and within individual investigators (coefficient of variability=72.1). The differences in the contact force between pulmonary vein sites were statistically significant ( p<0.0001).

Selected secondary outcomes:

Number of valid contact force records (stable contact force for 15 consecutive seconds)

529 valid records (90%) during mapping.

71% valid records during ablation.

Safety

n=34

Serious adverse events (SAE)

During the procedure: 4 patients with audible steam pops (12%).

3 months: 4 mild pulmonary vein stenosis (12%), 1 tamponade (3%), 1 bradycardia (3%), 1 groin bleeding (3%), 1 stroke (3%).

12 months: 9 SAE related to arrhythmia recurrence (26%)^a.

^a Note only 31 patients were followed‑up for the full 12‑month period due to 3 patients withdrawing consent prior to the study end, therefore the briefing authors conclude that 29% (9/31) of patients experienced serious adverse events.

The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study (Reddy et al. 2012)

Design

Prospective, single‑arm, multicentre, interventional study.

The study aimed to determine the relationship between contact force parameters during ablation for paroxysmal atrial fibrillation and clinical recurrence at 12‑month follow‑up.

Study participants were the same confirmed paroxysmal atrial fibrillation group reported in the TOCCATA study (Kuck et al. 2012).

Efficacy

Variable number of patients

Primary outcome:

procedural success

Procedural outcome: all pulmonary veins successfully isolated in 100% of study patients (34/34).

12‑month follow‑up: PVI considered successful in 53% (17/32). Atrial fibrillation recurrence defined as sustained atrial fibrillation, atrial flutter or atrial tachycardia for over 30 seconds.

Selected secondary outcomes:

Contact force

Number of valid contact force records (stable contact force for 15 consecutive seconds): 1017 of 1458 records (70%).

35% (351/1017) of ablation lesions were performed with low contact force (<10 g).

Overall, patients received ablations with an average contact force of 17.2±13.5 g.

The difference in contact force between pulmonary vein sites were statistically significant (p<0.001). On average, the highest contact force was applied at the right anterior inferior site, and the lowest contact force was applied at the left anterior inferior ridge and right carina site.

Intermittent contact (contact force reaching 0 g at every diastole for at least 200 ms) correlated with low contact force (p<0.001).

Subgroup analysis: all 5 patients treated with an average contact force <10 g were categorised as 'ablation unsuccessful' at 12 months. However 8/10 (80%) of patients treated with an average contact force >20 g were categorised in 'ablation successful'.

Force‑time integral

Mean FTI <500 gs predicted a success rate of 25% (2/8) at 12 months.

Mean FTI >1000 gs predicted a success rate of 60% (9/13), p=0.03.

Safety

Not reported

EFFICAS‑II: optimization of catheter contact force improves outcome of pulmonary vein isolation for paroxysmal atrial fibrillation (Kautzner et al. 2015)

Design

EFFICAS‑II study. Prospective single‑arm, multicentre, interventional study.

The aim of this study was to assess the impact of contact force guidance for an effective reduction PVI gaps prospectively, and to compare outcomes with the previous EFFICAS‑I study.

Efficacy

n=24

Primary outcome:

pulmonary vein isolation at 3 months

85% (77/91 pulmonary veins)

This was a significant increase from 72% (73/102) reported in the EFFICAS‑I study (p=0.037).

Selected secondary outcomes:

Contact force

Pulmonary vein segments with conduction gaps:

Minimum – 13.1 g

Average – 28.8 g

Successfully isolated pulmonary vein segments:

Minimum – 11.4 g (p=0.22)

Average – 9.2 g (p<0.01)

Contact force between 10 and 30 g was achieved in 68% of ablations, which is a significant increase from 49% reported in the EFFICAS‑I study (p<0.001).

Force‑time integral

Pulmonary vein segments with conduction gaps:

Minimum – 223 gs

Average – 868 gs

Successfully isolated pulmonary vein segments:

Minimum – 290 gs (p=0.48)

Average – 704 gs (p=0.03)

Force time integral greater than 400 gs was achieved in 78%, which is a significant increase from 55% in the EFFICAS‑I study (p<0.001).

Total number of ablations

Pulmonary vein segments with conduction gaps: 6

Successfully isolated pulmonary vein segments: 6 (p=0.52)

For equal setting of radiofrequency power, there was a 15% reduction in the number of ablations (1372 ablations in EFFICAS‑II vs. 1818 in EFFICAS‑I, p=0.05).

Safety

n=24

Patients reporting serious adverse events

8.3% (2/24 patients)

Tamponade: 8.3% (2/24 patients)

Abbreviations: FTI, Force‑time integral; g, grams; gs, gram‑seconds; n, number of patients; PVI, pulmonary vein isolation; SAE, serious adverse events.