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Trial registered on ANZCTR

Registration number
Ethics application status
Submitted, not yet approved
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Investigating the safety and efficacy outcomes of high power and short duration ablation for atrial fibrillation in comparison with current standard of lower power and longer duration ablation
Scientific title
High Power Short Duration (HPSD) versus Lower Power Longer Duration (LPLD) Atrial Fibrillation Ablation in Posterior Left Atrium and Hyperthermic Effects on EsophAgeal Tissue : A Prospective Single Centre Randomised Trial (the Hi-Lo HEAT Study)
Secondary ID [1] 299673 0
Universal Trial Number (UTN)
Trial acronym
HiLo HEAT Study
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Atrial fibrillation 315018 0
Condition category
Condition code
Cardiovascular 313352 313352 0 0
Other cardiovascular diseases

Study type
Description of intervention(s) / exposure
Patients will undergo AF ablation procedure as clinically indicated. This procedure is done under general anaesthesia by an interventional cardiac electrophysiologist. Access will be gained via right femoral vein with 4 sheaths placed. Diagnostic catheters are placed in the Coronary sinus and His bundle. Transesophageal echocardiogram is performed to exclude cardiac thrombus and to guide transseptal puncture. A circular mapping catheter and ablation catheter are placed in the left atrium via long sheaths following transseptal puncture access. The mapping catheter will be used to create a 3D map of the left atrium, which is integrated with pre-procedural CT images of the left atrium. Radiofreqeuency energy is applied using the ablation catheter to create the ablation lesions, with the aim being to perform pulmonary vein isolation. For this study, patients will be randomised to either lower power (25W) with longer duration (30 seconds) when ablating in the posterior wall of the left atrium, or high power ( 50W) with short duration (5 seconds). A multisensor esophageal temperature probe will be used to monitor for luminal temperature rises. The typical duration for an AF ablation is 3 hours, including anaesthetic preparation time.Following the AF ablation, patients will undergo an upper gastrointestinal endoscopy procedure which is done under sedation, to look for any evidence ofesophageal thermal injury. A case report form will be used to record all intraprocedural details from the AF ablation and also findings from the post ablation endoscopy. All patients will be followed up for 12 months after their ablation procedure. Anticoagulation is continued for at least 3 months after ablation, with cessation beyond that as per clinician decision. Anti-arrhythmic medications will be discontinued after ablation in paroxysmal AF patients, and at 3 months after ablation in persistent AF patients. Patients will be reviewed in the arrhythmia clinic at 3 and 12 months. Heart rhythm monitoring is performed either via AliveCor® electronic rhythm monitoring system, or 24 Hr holters. Follow-up 24-day holter monitoring will be performed at 3,6, 9 and 12 months. Patients will be requested to complete the AFEQT questionnaire at 6 months and 12 months
Intervention code [1] 315937 0
Treatment: Devices
Comparator / control treatment
Lower power longer duration ablation
Control group

Primary outcome [1] 321829 0
Esophageal thermal injury
Timepoint [1] 321829 0
24 hours following intervention through routine post ablation endoscopy
Primary outcome [2] 321830 0
Significant intraluminal temperature rise during ablation, defined as :
o Number of temperature spikes more than or equal to 39ºC
o Number of steep temperature rises of more than 0.5 -1 degrees within 5 seconds
o Number of steep temperature rises of more than 1 degrees within 5 seconds
o Cumulative amount of time in which temperature was more than or equal to 38ºC

Intraluminal temperature is measured using a multisensor temperature probe ( S -Cath, Circa Scientific) placed in the esophagus
Timepoint [2] 321830 0
Secondary outcome [1] 376386 0
Radiofrequency energy amount, which is derived from the ablation console (NAVx or CARTO)
Timepoint [1] 376386 0
Immediately after
Secondary outcome [2] 376387 0
First pass pulmonary vein isolation (PVI) rate , with or without posterior wall isolation (PWI) rate. This is measured using the mapping catheter used intraprocedurally which is placed into the pulmonary vein / onto the posterior wall

Timepoint [2] 376387 0
Secondary outcome [3] 376388 0
Acute procedural complications which include:
-cardiac perforation / tamponade which is assessed on clinical examination and confirmed on echocardiogram
-stroke, which is assessed on clinical examination and confirmed on brain imaging
- groin complication, which includes bleeding, bruising, and vascular damage. This is assessed on clinical examination and confirmed on leg ultrasound

Delayed procedural complication, which include
- Pulmonary vein stenosis - this is assessed based on participant reported symptom of breathlessness and confirmed on CT venogram
-Atrioesophageal fistula - this is assessed based on participant reported symptom of dysphagia/ odynophagia, physical examination looking for fevers , and confirmed on CT scan of the chest
Timepoint [3] 376388 0
Intraprocedure to 12 months follow up
Patients are reviewed in the arrhythmia clinic at routinely at 3 months and 12 months. Additional clinical review within this time frame will be as per treating clinician discretion
Secondary outcome [4] 376389 0
Single radiofrequency (RF) ablation procedure success rate off anti-arrhythmic drugs at 12 months. Participants will have their rhythm monitored to look for any atrial arrhythmia (including atrial fibrillation) recurrence using either 3 monthly 24 holter monitors or the Alive Cor cardiac monitoring device (where patients will send their ECGs daily). Patients will also have their ECGs recorded durng their clinical follow ups.
Timepoint [4] 376389 0
12 months post ablation
Secondary outcome [5] 376680 0
Procedural duration time. This will be based on the stated start and end times on the medical records
Timepoint [5] 376680 0
Immediately after procedure
Secondary outcome [6] 376682 0
Fluoroscopy time, which is derived from the Phillips X ray interventional system in the cathlab
Timepoint [6] 376682 0
Immediately after procedure
Secondary outcome [7] 376923 0
Radiofrequency energy time, which is derived from the ablation console (NAVx or CARTO)
Timepoint [7] 376923 0
Immediately after
Secondary outcome [8] 376924 0
Effects of ablation on the quality of life of participants will be assessed using the AFEQT questionnaire
Timepoint [8] 376924 0
6 and 12 months after the ablation

Key inclusion criteria
1. Patients aged more than / equal to 18 years old
2. Patients undergoing a first-time ablation procedure for AF
3. Patients with symptomatic AF that is refractory to at least one antiarrhythmic medication
4. Patients must be able and willing to provide written informed consent to participate in this investigation
5. Patients must be willing and able to comply with all peri-ablation and follow- up requirements
Minimum age
18 Years
Maximum age
75 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
1. Patients with long-standing persistent AF - defined as a sustained episode lasting more than 3 years
2. Patients for whom cardioversion or sinus rhythm will never be attempted/pursued
3. Patients with AF felt to be secondary to an obvious reversible cause
4. Left atrium thrombus
5. Previous AF ablation
6. Severe valvular heart disease
7. Known esophageal disorder / GORD
8. Patients with contraindications for taking anticoagulation therapy
9. Patients with creatinine >200 ml/min or end stage renal / liver impairment
10. Pregnancy
11. Diagnosis of hypertrophic cardiomyopathy.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Central randomisation by computer
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Simple randomisation using a randomisation table created by computer software (i.e. computerised sequence generation)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s

The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Other design features
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
This study is designed to demonstrate non inferiority against standard lower power longer duration RF ablation. A recent meta-analysis had reported a pooled prevalence of endoscopically detected esophageal lesion of 11% (95% CI 6.3-15% ; range 2.2- 21%)(25). Assuming an ETI rate of 5% in the high power short duration cohort, the minimum sample size needed per treatment arm would be 33 patients to exclude a difference in favour of the standard group by more than 5% with a power of 80% (significance level of 5%).

Recruitment status
Not yet recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 15065 0
The Alfred - Melbourne
Recruitment postcode(s) [1] 28359 0
3004 - Melbourne

Funding & Sponsors
Funding source category [1] 304147 0
Self funded/Unfunded
Name [1] 304147 0
Professor Peter Kistler
Address [1] 304147 0
Alfred Health
55 Commercial Road
Melbourne 3004 Victoria
Country [1] 304147 0
Funding source category [2] 304297 0
Name [2] 304297 0
Cardiology Department, Alfred Hospital
Address [2] 304297 0
55 Commercial Road, Melbourne 3004 Victoria
Country [2] 304297 0
Primary sponsor type
Alfred Health
55 Commercial Road, Melbourne 3004 Victoria
Secondary sponsor category [1] 304378 0
Name [1] 304378 0
Address [1] 304378 0
Country [1] 304378 0

Ethics approval
Ethics application status
Submitted, not yet approved
Ethics committee name [1] 304629 0
Alfred Health Ethics and Research Governance Committee
Ethics committee address [1] 304629 0
55 Commercial Road, Melbourne 3004 Victoria
Ethics committee country [1] 304629 0
Date submitted for ethics approval [1] 304629 0
Approval date [1] 304629 0
Ethics approval number [1] 304629 0

Brief summary
Catheter based atrial fibrillation (AF) ablation is an effective treatment option for AF patients who are intolerant or who do not respond to medications. Ablation using radiofrequency energy in the back wall (posterior wall) of the left atrium is associated with a risk of causing esophageal thermal injury (ETI). Current strategies to minimise the risk of ETI include reducing the ablation power setting to 25 Watts and using an esophageal temperature probe. Recent studies have shown that the use of high power (50 Watts) but shorter duration (HPSD) ablation results in more effective AF lesion formation with no increase in complication rates, including rates of ETI. This single center randomised trial is designed to compare HPSD ablation to standard lower power longer duration (LPLD) ablation and the effects on ETI rates. Patients with paroxysmal or persistent AF undergoing their first AF ablation procedure at the Alfred Hospital will be recruited and randomised into the 2 treatment arms. A multisensor esophageal temperature probe will be used in all cases. All participants will undergo an endoscopy within 24 hours after their ablation to look for evidence of ETI, with 12 months of follow up after. We expect the study to show that HPSD ablation is non- inferior to LPLD ablation in terms of ETI, with significantly lower procedural times and exposure to radation
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 97642 0
Prof Peter Kistler
Address 97642 0
Alfred Health
55 Commercial Road, Melbourne 3004 Victoria
Country 97642 0
Phone 97642 0
+61 03 90762000
Fax 97642 0
Email 97642 0
Contact person for public queries
Name 97643 0
Dr David Chieng
Address 97643 0
Alfred Health
55 Commercial Road, Melbourne 3004 Victoria
Country 97643 0
Phone 97643 0
+61 0390762000
Fax 97643 0
Email 97643 0
Contact person for scientific queries
Name 97644 0
Dr David Chieng
Address 97644 0
Alfred Health
55 Commercial Road, Melbourne 3004 Victoria
Country 97644 0
Phone 97644 0
+61 0390762000
Fax 97644 0
Email 97644 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No/undecided IPD sharing reason/comment
What supporting documents are/will be available?
Informed consent form
How or where can supporting documents be obtained?
Type [1] 5495 0
Informed consent form
Citation [1] 5495 0
Link [1] 5495 0
Email [1] 5495 0
Other [1] 5495 0
Summary results
No Results