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Heart, Lung and Circulation Abstracts S1172008;17S:S1–S209

Conclusion: Despite equally severe LV dysfunction,patients without clinical SMVT had significantly less totaland dense scar, fractionated electrograms, LP, and VLP.These differences in substrate are likely to play an impor-tant role in SMVT arrhythmogenesis.

doi:10.1016/j.hlc.2008.05.279

279Left Ventricular Substrate in Dilated CardiomyopathyPatients With and Without Ventricular Tachycardia

Haris Haqqani ∗, Kurt Roberts-Thomson, RichardSnowdon, Caroline Medi, Richard Balasubramaniam,Paul Sparks, Jitendra Vohra, Jonathan Kalman, JosephMorton

Royal Melbourne Hospital, Parkville, Victoria, Australia

Background: Left ventricular (LV) endocardial scar may bea component of the substrate for sustained monomorphicventricular tachycardia (SMVT) in dilated cardiomyopathy(DCM). We studied endocardial scarring in DCM patientswith and without clinical SMVT.Methods: Electroanatomical mapping (mean 400 points) ofthe LV endocardium was performed in eight DCM patientswithout clinical SMVT (group 1). They were compared to6 DCM patients with spontaneous SMVT (group 2). Densescar was defined as bipolar voltage <0.5 mV. FractionatedenoRmt2wI0psgp3pCuoDeb

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280Impedance Mapping for Identification of Ventricular Scarduring Ablation of Ventricular Tachycardia

Andrew Liu 1,∗, Magdy Basta 2, Ratika Parkash 2, MartinGardner 2, Amir Abdelwahab 2, John Sapp 2

1 Fremantle Hospital, Perth, Western Australia, Australia;2 Queen Elizabeth II Health Sciences Centre, Halifax, Nova Sco-tia, Canada

Background: During catheter ablation of ventriculartachycardia, differentiating scar from normal myocardiumis crucial. Bipolar signal amplitude (voltage) mapping ismost commonly used. Low impedances are recorded fromventricular scar in an animal model, but its relationship tovoltage in humans is unknown.Method: Eleven patients with left ventricular VT, (sixpost-MI, four idiopathic, one epicardial) underwent 3Delectroanatomic mapping. At each location, voltage andimpedance were recorded. A voltage <1.5 mV was usedto define areas of scar. Voltage was correlated withimpedance and receiver-operating curves (ROC) weregenerated to identify an impedance cut-off with optimaldiscrimination of low voltage for the group and individu-ally. This was then used to compare scar area as assessedby voltage and impedance.Results: With epicardial mapping, there was no correla-tion between impedance and voltage (R = 0.02). A total of2lwv0iam9IvCmt

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lectrograms were multi-component low-amplitude sig-als and very late potentials (VLP) were electrogramsccurring >100 ms after the QRS.esults: Patients in both groups were well matched forean age, LV diameter (66 mm vs. 68 mm), ejection frac-

ion (24% vs. 21%) and LV surface area (238 cm2 vs.78 cm2). Group 1 patients had minimal dense scarringith median area of 3.4 cm2 (1.4%), patchily distributed.

n group 2, there were large variations in scarring (range.4–30%) with median area 11 cm2 (8.4%). Three of sixatients had no confluent areas but three had extensivecarring. There was no difference in fractionated electro-ram prevalence (15% vs. 27% of total sampled points,= 0.21). VLPs were rarely seen (2/8 pts in group 1 and/6 in group 2; mean number of VLPs per pt 0.9 vs. 2.6,= ns).onclusion: Extensive dense LV endocardial scarring isncommon in DCM and was not seen in any patient with-ut clinical SMVT. The endocardial substrate for SMVT inCM appears to be heterogeneous and this suggests that

picardial scarring and other arrhythmia mechanisms maye important.

oi:10.1016/j.hlc.2008.05.280

106 endocardial points were analyzed. Impedance corre-ated moderately well with voltage (R = 0.62). Impedanceas higher in regions with normal vs. low voltage (120 ± 16s. 101 ± 11, p < 0.0001). The area under the ROC curve was.845 (95% CI 0.83–0.86; p < 0.0001). The best discriminat-ng impedance value of 108 had a sensitivity of 74% and

specificity of 79%. Scar area estimated by impedanceapping was similar to voltage mapping (110 ± 95 cm2 vs.

2 ± 78 cm2, p = 0.64), but had wide confidence intervals.ndividually optimised impedance cutoffs had significantariation (108.7 ± 8.4, range 101.5–125.5).onclusions: Impedance mapping correlates with voltageapping, but no single impedance cutoff value will iden-

ify areas of low voltage in all patients.

oi:10.1016/j.hlc.2008.05.281

81ptimisation and Validation of Noncontact Mapping ofcar in an Ovine Model of Chronic Myocardial Infarction

MI)

im Pouliopoulos ∗, Gopal Sivagangabalan, Kaimin Huang,ony Barry, Juntang Lu, Pramesh Kovoor

Westmead Hospital, Sydney, NSW, Australia

ntroduction: Noncontact sinus rhythm (SR) mapping isimited in identifying scar, the border of which could berrythmogenic. Dynamic substrate mapping (DSM) is aovel method for mapping critical scar borders. We devel-ped an alternative method for calculating DSM (ADSM).IM: To validate DSM and ADSM using functional andistological assessment.