Cardiovascular Journal of Africa: Vol 26 No 4 (July/August 2015)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 4, July/August 2015

166

AFRICA

patients with/or without AF recurrence. The secondary endpoint

was other potential predictors of recurrent atrial tachycardia of

more than 30 seconds during mid-term follow up of six months

without a blanking period.

Methods

The study population consisted of 57 consecutive patients who

underwent PVI with the cryo-balloon technique for 12-lead

verified, symptomatic and drug-refractory paroxysmal AF.

Patients whose episodes of AF had self-terminated within seven

days were defined as paroxysmal AF. The indication for ablation

was based on the guidelines.

Detailed inclusion and exclusion

criteria for patients are outlined in Table 1.

Symptomatic severity of the patients was recorded according

to the European Heart Rhythm Association (EHRA) score.

CHA

-VASc scores were calculated for each patient based

on the relevant guidelines.

Written informed consent was

obtained from all patients before the procedure. The local ethics

committee approved the study.

Pre-procedural evaluation: standard transthoracic echo-

cardiography (TTE) was performed in all patients to evaluate left

atrium diameters and to rule out structural abnormality. In all

patients, left atrial thrombus was ruled out by transoesophageal

echocardiography (TEE) prior to the procedure. All patients

were anticoagulated with warfarin to maintain an international

normalised ratio (INR) of 2–3 for at least four weeks prior to

the procedure. Warfarin was interrupted before the procedure.

The procedures were done if the INR value was

1.5. Anti-

arrhythmic drugs were discontinued five half-lives before the

procedure.

Blood sampling and biomarker measurements: blood samples

were obtained during venous puncture before the procedure and a

further one and 24 hours after ablation. The blood level of hsTnI

was measured in frozen EDTA plasma samples using the current

version of the AccuTnI assay (Beckman Coulter Inc, Fullerton,

CA, USA). Serum CK activity was determined using an analyser

Integra (Roche). The reference ranges in our laboratory for the

cardiac markers were as follows: CK-MB mass, 0.5–5 ng/ml;

myoglobin, 0–113 ng/ml; and hsTnI, 0.0–0.06 ng/ml. Cardiac

hsTnI cut-off values for the diagnosis of myocardial infarction

(0.06 ng/ml) were accepted as pathologically increased.

Ablation procedure: the procedure was performed under

local anesthesia. Trans-septal punctures were performed

under fluoroscopic guidance only. After trans-septal puncture,

intravenous heparin was used to maintain an activated clotting

time of 300 to 400 seconds. A single or double trans-septal

puncture was performed using a conventional circumferential

mapping catheter (Inquiry

, Optima

, St Jude Medical, Sylmar,

CA, USA) or the customised mapping catheter (Achieve

Medtronic, Minneapolis, MN, USA). Positioning of the 28-mm

cryo-balloon catheter (Arctic Front Advance

, Medtronic,

Minneapolis, MN, USA) was achieved using a guidewire and

a 12-Fr steerable sheath (Flexcath Medtronic Minneapolis,

MN, USA). While delivering cryo-energy to the right PVs, a

6-F decapolar coronary sinus (CS) catheter or a quadripolar

diagnostic catheter was positioned in the superior vena cava for

phrenic nerve stimulation.

Before each freeze, the grade of occlusion (semi-quantitative

scale from 1

poor occlusion to 4

perfect occlusion) was

quantified with an injection of contrast medium.

After

confirmation of PV occlusion by contrast injection, the

240-second freezing cycle was initiated. After two freezing cycles,

PVI was assessed using a circumferential mapping catheter.

If PVI was not achieved within five attempts, the customised

mapping catheter was exchanged for a stiffer wire (Amplatz

Ultra Stiff, COOK Medical Inc). Isolation of PVs was defined

as the presence of both entrance and exit block.

In all patients, rapid atrial pacing from the distal tip of the

CS catheter was used to induce AF after the procedure. If AF

could not be induced or sustained for longer than one minute

by rapid atrial pacing, an infusion of isoproterenol (10 mcg/

min) was used to sustain AF. Complex fractionated electrogram

(CFE) mapping was performed to detect any focal source except

for PVs, if the AF persisted for more than one minute. CFE

mapping using an automated algorithm (Ensite NavX, St Jude

Medical) was performed in the LA, CS and right atrium. The

technique for CFE mapping using automated mapping software

has been described and validated previously.

Patients in whom

CFE was detected outside the LA were excluded from the study.

For RF ablation of CFE, an open irrigated-tip catheter with

a 3.5-mm tip electrode (ThermoCool, Biosense Webster) was

used in conjunction with a three-dimensional electro-anatomical

mapping system (NavX Fusion, St Jude Medical). The energy of

the RF was delivered with power of up to 35 W and a maximum

temperature of 43°C. The endpoint for CFE ablation was (1)

elimination of all CFE sites in the LA or termination of AF, and

(2) non-inducibility of AF post ablation with the same protocol.

Post-procedural evaluation: TTE was performed immediately

after the procedure to exclude the presence of pericardial effusion.

All patients were followed up for at least 12 hours in the intensive

care unit. Patients were then discharged provided that their

clinical status was stable. Oral anticoagulation was initiated on

the evening of ablation unless pericardial effusion was detected,

and continued for at least three months after the procedure. The

patients presenting with arrhythmia-related symptoms in the first

Table 1. Study inclusion and exclusion criteria

Inclusion criteria

• Patients age

≥

18 years

• Paroxysmal AF (AF that terminates spontaneously or with intervention

within 7 days of onset)

• Symptomatic and drug refractory (at least one anti-arrhythmic) AF

• At least three episodes of AF must have been documented by ECG or

Holter before the procedure

• Patients must be on continuous anticoagulation with warfarin (INR

2–3) for

4 weeks prior to the ablation

• Patients must be able and willing to provide written informed consent to

the procedure

Exclusion criteria

• Previous abdominal surgical procedures

• History of either acute or chronic neuropathies

• Usage of drugs that affect gastrointestinal motility

• Persistent or permanent AF

• Inadequate anticoagulation as defined in the inclusion criteria

• Left atrial thrombus on transoesophageal echo prior to the procedure

• Contra-indications to any anticoagulant

• Previous AF ablation procedure

• Left atrial size

55 mm

• Left ventricular ejection fraction

30%

• Congestive heart failure with New York Heart Association class IV