Caroline Medi

Royal Melbourne Hospital, Melbourne, Victoria, Australia

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Publications (68)200.78 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: -Successful arrhythmia ablation normalizes ejection fraction (EF) in tachycardia-mediated cardiomyopathy (TMC), but recurrent heart failure and late sudden death have been reported. The aim of this study was to characterize the left ventricle (LV) of TMC patients long after definitive arrhythmia cure. -Thirty-three patients with a history of successfully ablated incessant focal atrial tachycardia 64±36 months prior, and 20 healthy controls were recruited. At ablation, 18 patients had EF<50% (AT-Low EF) that recovered within 3 months from 37±12 to 56±4% (p<0.001), while 15 patients had EF>55% (AT-Normal EF). No subjects had EF of 50% to 55%. Subjects underwent echocardiography with speckle tracking and contrast-enhanced cardiac magnetic resonance imaging (CMR) with ventricular T1 mapping as an index of diffuse fibrosis. CMR was performed using a clinical 1.5-T scanner and 0.2 mmol/kg gadolinium-DTPA for contrast. Subject characteristics were similar across the 3 groups. Compared to AT-Normal EF patients and controls, AT-Low EF patients had lower EF (60±6 vs 64±4 and 65±4%, p<0.05), greater indexed LV end-diastolic volume (102±34 vs 84±14 and 85±16 ml/m(2), p<0.05), and greater indexed LV end-systolic volume (41±11 vs 31±7 and 3±8 ml/m(2), p<0.01) on CMR. Compared to controls, AT-Low EF patients had reduced global LV corrected T1 time (442±53 vs 529±61, p<0.05) consistent with diffuse fibrosis. -TMC patients exhibit differences in LV structure and function including diffuse fibrosis long after arrhythmia cure, indicating that recovery is incomplete.
    Circulation Arrhythmia and Electrophysiology 07/2013; 6(4). DOI:10.1161/CIRCEP.113.000681 · 4.51 Impact Factor
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    ABSTRACT: Atrial fibrillation (AF) and systolic heart failure (HF) frequently coexist. Restoration of sinus rhythm by catheter ablation may result in a variable improvement in left ventricular (LV) function. Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging identifies irreversible structural change and may predict incomplete recovery of LV function. We prospectively selected AF and symptomatic HF patients without LV LGE and report the impact of AF ablation on LV function. Patients with AF and symptomatic HF (LV EF<50%) resistant to at least one antiarrhythmic drug and prior electrical cardioversion underwent contrast-enhanced CMR. LGE negative patients underwent pulmonary vein isolation and left atrial roof line with continued antiarrhythmic medications until follow-up CMR 6 months post-ablation. Sixteen patients (aged 52±11 years, mean AF duration 37±39 months, LA size 44±13 ml/m(2)) underwent AF ablation. At 6 months, 15 of 16 patients maintained sinus rhythm and underwent CMR. LV EF increased from 40±10% at baseline to 60±6% (p<0.001) and LV end systolic volume index decreased from 52±12 to 36±9 ml/m(2) (p<0.001). Left atrial size decreased from 44±13 to 36±11 ml/m(2) (p<0.01). In patients with AF and LV dysfunction in the absence of LGE on CMR, ventricular function normalizes following the restoration of sinus rhythm. CMR may assist in the selection of AF-HF patients most likely to benefit from catheter ablation.
    Heart rhythm: the official journal of the Heart Rhythm Society 06/2013; 10(9). DOI:10.1016/j.hrthm.2013.06.019 · 5.08 Impact Factor
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    ABSTRACT: OBJECTIVES: This study sought to determine whether post-operative neurocognitive dysfunction (POCD) occurs following AF ablation. BACKGROUND: Ablation for atrial fibrillation (AF) is a highly effective strategy, however the risk of transient ischaemic attack and stroke is approximately 0.5-1%. In addition MRI studies report a 7-14% incidence of silent cerebral infarction. Whether cerebral ischaemia results in POCD after AF ablation is not well-established. METHODS: The study included 150 patients: 60 patients undergoing ablation for paroxysmal AF (PAF); 30 patients undergoing ablation for persistent AF n=30 (PeAF) and 30 patients undergoing ablation for supraventricular tachycardia (SVT) were compared to a matched non-operative control group of patients with AF awaiting radiofrequency ablation (n=30). Patients were administered 8 neuropsychological tests administered at baseline and at 2 days and 3 months post-operatively. Tests were administered at the same time-points to the non-operative control group. Reliable change index was used to calculate POCD. RESULTS: The incidence of POCD at day 2 post-procedure was 28% in patients with PAF; 27% in patients with PeAF; 13% in patients with SVT; and 0% in AF control patients (p=0.007). At day 90, the incidence of POCD in patients with PAF was 13%, 20% in patients with PeAF; 3% in patients with SVT, and 0% in AF control patients (p=0.03). When analyzing the 3 procedural groups together, 29/120 (24%) patients manifest POCD at day 2 and 15/120 (13%) at day 90 post ablation procedure; p=0.029. On univariate analysis increasing LA access time was associated with POCD at day 2 (p=0.04) and day 90 (p=0.03) CONCLUSIONS: Ablation for atrial fibrillation is associated with a 13-20% incidence of POCD in patients with AF at long-term follow up. These results were seen in a population of predominantly CHADS2 0-1 patients who represent the majority of patients undergoing AF ablation. The long-term implications of these subtle changes require further study.
    Journal of the American College of Cardiology 05/2013; 62(6). DOI:10.1016/j.jacc.2013.03.073 · 16.50 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S129. DOI:10.1016/j.hlc.2012.05.323 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S131-S132. DOI:10.1016/j.hlc.2012.05.331 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S131. DOI:10.1016/j.hlc.2012.05.329 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S251. DOI:10.1016/j.hlc.2012.05.616 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S99. DOI:10.1016/j.hlc.2012.05.250 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2012; 21:S139. DOI:10.1016/j.hlc.2012.05.351 · 1.44 Impact Factor
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    ABSTRACT: Left Septal Atrial Tachycardias. Objective: The objective was to characterize the electrocardiographic and electrophysiological features of focal atrial tachycardia (FAT) originating from the left septum (LS). Background: FAT is recognized to occur at predefined anatomic locations rather than randomly throughout the atria. We describe the ECG and EP features of ATs originating from the LS as an important site for apparent perinodal tachycardias. Methods: Nine patients presenting with LS FAT from a consecutive series of 384 underwent EP/RFA for symptomatic FAT. Results: The mean age was 56 ± 12 years; 7 female with symptoms for 36 ± 28 months. P wave morphology (PWM) was negative/positive in lead V1 and across the precordial leads and negative or negative/positive in inferior leads in all patients. Tachycardia was incessant in 6 out of 9 patients with a mean tachycardia cycle length 421 ± 56 milliseconds. His A was ahead of P wave in all patients (mean −15 ± 5 milliseconds) and earlier than CS proximal (mean 4 ± 9 milliseconds). Successful acute focal ablation achieved at a mean of 31 ± 12 milliseconds ahead of P wave with no recurrences at a mean follow-up of 30 ± 28 months. Conclusion: Although the left septum is an uncommon site for focal AT an awareness of this location for harboring foci is particularly important when mapping apparently right-sided septal tachycardias. (J Cardiovasc Electrophysiol, Vol. 24, pp. 413-418, April 2013)
    Journal of Cardiovascular Electrophysiology 11/2012; 24(4). DOI:10.1111/jce.12049 · 2.96 Impact Factor
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    ABSTRACT: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in human beating hearts. AF initiates self-perpetuating changes in electrophysiology, structure and functional properties of the atria, a phenomenon known as atrial remodeling. Hypertension, heart failure, valvular heart disease, sleep apnea, congenital heart disease are well known risk factors for AF that contribute to the development of atrial substrate. There is some evidence that reversal of atrial remodeling is possible with correction of antecedent conditions, however the timing of the intervention or upstream therapy may be critical. This review will describe the pathophysiology of atrial remodeling as it pertains to AF. We will describe components of remodeling including changes in atrial refractoriness, conduction and atrial structure, in addition to autonomic changes and anatomic factors that predispose to remodeling. We will discuss our current understanding of the electrophysiological changes that contribute to AF persistence. We will describe nature of atrial and pulmonary vein remodeling in the context of different forms of AF, with and without predisposing risk factors. We will describe the nature of remodeling over time following therapeutic interventions such as AF ablation in order to show that it does not necessarily improve and may worsen.
    Progress in Biophysics and Molecular Biology 08/2012; 110(2-3). DOI:10.1016/j.pbiomolbio.2012.07.011 · 2.27 Impact Factor
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    ABSTRACT: Atrial Remodeling in Atrial Flutter. Introduction: Atrial fibrillation (AF) and atrial flutter (AFL) are related arrhythmias with common triggers, yet in individual patients either AF or AFL often predominates. We performed detailed electrophysiologic (EP) and electroanatomic (EA) studies of the right atrium (RA) in patients with AF and AFL to determine substrate differences that may explain the preferential expression of AF/AFL in individual patients. Methods: Patients with AF (n = 13) were compared to patients with persistent AFL (n = 10). Detailed studies were performed, and 3-dimensional electroanatomic mapping studies were created and the RA was divided into 4 segments for regional analysis. Global, septal, lateral, anterior, and posterior segments were compared for analysis of: bipolar voltage; proportion of low-voltage areas and areas of electrical silence; conduction times; and proportion of abnormal signals (fractionated signals and double potentials). Results: Compared to patients with AF, patients with AFL had (1) lower bipolar voltage and an increase in the proportion of low-voltage areas; (2) an increase in the proportion of complex signals; and (3) prolongation of activation times. Conclusions: Patients with AFL showed more advanced remodeling than patients with AF with slowed conduction, lower voltage areas with regions of electrical silence, and a greater proportion of complex signals, particularly in the posterior RA. These changes facilitate the stabilization of AFL and may explain why some patients are more likely to develop AFL as a sustained clinical arrhythmia. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1067-1072, October 2012).
    Journal of Cardiovascular Electrophysiology 04/2012; 23(10):1067-72. DOI:10.1111/j.1540-8167.2012.02364.x · 2.96 Impact Factor
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    ABSTRACT: Pulmonary hypertension (PH) is common to a range of cardiopulmonary conditions and is associated with atrial arrhythmias. However, little is known of the isolated atrial effects of PH and right atrial dilatation (RA) in humans. To avoid the confounding effects of PH-associated disease states, we performed detailed electrophysiological (EP) and electroanatomic (EA) mapping of the RA in patients with idiopathic PH. Eight PH patients (mean pulmonary arterial [PA] pressure 39.0 ± 15.8 mmHg) and 16 age-matched controls (mean PA pressure 11.5 ± 4.1 mmHg, P < 0.0001) were studied. Corrected sinus node recovery times (cSNRT), atrial effective refractory periods (ERPs), conduction delay at the crista terminalis (CT), and inducibility of atrial fibrillation (AF) were evaluated. EA mapping (pacing cycle length 600 and 300 milliseconds) was performed to determine RA global and regional voltage, conduction velocities, atrial activation times, fractionated electrograms and double potentials. Patients with PH demonstrated a prolongation in cSNRT without significant change in atrial ERP and an increase in AF inducibility. PH was associated with lower tissue voltage (1.8 ± 0.4 mV in PH vs 2.2 ± 0.4 mV in controls, P = 0.02), increased low voltage areas (13.7 ± 8.2% in PH vs 6.2 ± 3.7% in controls, P < 0.01) and the presence of electrically silent areas. Conduction velocities were slower (global 67.3 ± 5.6 cm/s vs 92.8 ± 4.0 cm/s, P < 0.001) and fractionated electrograms and double potentials were more prevalent (14.7 ± 4.4% vs 6.3 ± 4.1, P < 0.01) in PH compared with controls, respectively. Idiopathic PH is associated with RA remodeling characterized by: generalized conduction slowing with marked regional abnormalities; reduced tissue voltage; and regions of electrical silence. These changes provide important insights into the isolated effects of PH fundamental to a range of clinical conditions associated with AF.
    Journal of Cardiovascular Electrophysiology 01/2012; 23(6):614-20. DOI:10.1111/j.1540-8167.2011.02255.x · 2.96 Impact Factor
  • L. Ling · A. Ellims · G. Lee · A. Teh · C. Medi · D. Kaye · A. Tayor · P. Kistler
    Heart, Lung and Circulation 12/2011; 20. DOI:10.1016/j.hlc.2011.05.249 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2011; 20:S97. DOI:10.1016/j.hlc.2011.05.243 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2011; 20. DOI:10.1016/j.hlc.2011.05.253 · 1.44 Impact Factor
  • Heart, Lung and Circulation 12/2011; 20. DOI:10.1016/j.hlc.2011.05.264 · 1.44 Impact Factor
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    ABSTRACT: Whether curative ablation can prevent progression of the atrial electroanatomic remodeling associated with atrial fibrillation (AF) is not known. The purpose of this study was to determine whether successful radiofrequency ablation (RFA) of AF can prevent progression of the atrial substrate associated with AF. Detailed right atrial electroanatomic maps from 11 patients without apparent structural heart disease undergoing RFA of AF at baseline and ≥6 months following successful RFA were compared to 11 control patients undergoing electrophysiologic evaluation of supraventricular tachycardia. Bipolar voltage, conduction, effective refractory periods (ERPs), and signal complexity were assessed. At baseline compared with the control group, the AF group demonstrated (1) lower voltage (P <.001); (2) slowed conduction (P = .005); (3) more prevalent complex signals (P <.001); (4) prolonged regional refractoriness (P <.05), and (5) left atrial dilation (P = .01). At 10 ± 13 month follow-up, the AF group demonstrated the following compared to baseline: (1) lower voltage (P <.05); (2) either no improvement or further slowing of conduction; (3) further prolongation of regional refractoriness (P <.05); and (4) reversal of left atrial dilation (P <.05). Patients with lone AF demonstrate evidence of an abnormal atrial substrate at baseline compared to control patients without AF. This substrate does not appear to reverse even after successful catheter ablation. These findings may have implications for long-term outcomes of ablation and for timing of ablative intervention.
    Heart rhythm: the official journal of the Heart Rhythm Society 11/2011; 9(4):473-80. DOI:10.1016/j.hrthm.2011.11.013 · 5.08 Impact Factor
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    ABSTRACT: Increasing age is a significant risk factor for developing atrial fibrillation (AF). Pulmonary vein (PV) triggers are critical in the mechanism of AF, but little is known of the substrate changes that occur within the PVs with ageing. Therefore, we sought to identify whether ageing is associated with electroanatomic changes within the pulmonary veins. Twenty-five patients undergoing ablation for left-sided supraventricular tachycardia had high-density 3D electroanatomic maps of all four PVs created. Patients were divided into two groups: group 1 aged <50 years and group 2 aged >50 years. Mean-voltage (MV), % low-voltage (LV < 0.5 mV), conduction, signal complexity, and PV muscle sleeve length and diameter were assessed. Age was 33 ± 8 vs. 66 ± 8 years for groups 1 and 2, respectively (P < 0.001). Group 2 demonstrated: (i) lower MV within the PVs (1.66 ± 1.1 vs. 1.88 ± 1.1 mV, P < 0.001); (ii) increased % LV (5.0 vs. 1.1%, P < 0.001), and increased voltage heterogeneity within the PVs (65 ± 14 vs. 55 ± 8%, P < 0.05); (iii) regional and global conduction slowing in the PVs; and (iv) increased % complex signals within the PVs (1.4 vs. 0.4%, P = 0.009). There was no difference in PV sleeve length or diameter. Increasing age is associated with PV electroanatomic changes characterized by a significant reduction in PV voltage, conduction slowing, and increasing signal complexity. These observations provide new insights into the potential mechanisms behind the increased prevalence of AF with advancing age.
    Europace 08/2011; 14(1):46-51. DOI:10.1093/europace/eur275 · 3.67 Impact Factor
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    ABSTRACT: Mapping of atrial fibrillation (AF) involves identification of low-voltage regions associated with complex fractionated electrograms (CFE) which theoretically represent abnormal substrate and targets for ablation. Whether low-voltage CFE areas also identify abnormal substrate during paced rhythm is unknown. Twelve patients with persistent AF undergoing ablation of AF had high-density three-dimensional electroanatomic maps created during AF and paced rhythm (24 maps) and the mean voltage during AF and paced rhythm was compared for eight segments of the left atrium (LA). The following were correlated during AF and paced rhythm: regional mean voltage; %low voltage (defined as <0.5 mV); and extent of CFE. In addition, the relationship between the extent of CFE in AF: (i) %low voltage and (ii) conduction during paced rhythm were determined. Mean voltage was lower during AF than paced rhythm for all regions and globally (0.7 ± 0.2 mV vs. 2.1 ± 0.6 mV, P < 0.001). The regional and overall %low voltage of the LA was greater during AF than paced rhythm (53 ± 19% vs. 9 ± 2%, P < 0.001). There was no correlation between mean voltage or %low voltage during AF and paced rhythm. Complex fractionated electrograms were prevalent throughout all regions during AF, but did not correlate with %low voltage, fractionation, or slowed conduction during paced rhythm. Areas of CFE and low voltage recorded during AF frequently demonstrate normal atrial myocardial characteristics (normal conduction, electrograms, and voltage) during sinus rhythm. Therefore, AF CFE sites do not necessarily identify regions of an abnormal atrial substrate. However, this does not exclude the possibility that CFE might identify a focal driver or source occurring in a region of normal atrial myocardium.
    Europace 06/2011; 13(12):1709-16. DOI:10.1093/europace/eur197 · 3.67 Impact Factor

Publication Stats

486 Citations
200.78 Total Impact Points


  • 2008–2013
    • Royal Melbourne Hospital
      • Department of Nephrology
      Melbourne, Victoria, Australia
  • 2008–2012
    • University of Melbourne
      • Department of Medicine
      Melbourne, Victoria, Australia
  • 2011
    • Alfred Hospital
      Melbourne, Victoria, Australia
  • 2010
    • Concord Hospital
      Concord, New Hampshire, United States
    • University of Adelaide
      Tarndarnya, South Australia, Australia
  • 2007–2010
    • Concord Repatriation General Hospital
      Sydney, New South Wales, Australia