C A Alferness

Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia

Are you C A Alferness?

Claim your profile

Publications (44)157.15 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of digoxin on ventricular response during atrial fibrillation (API and consequent effects on arrhythmic symptoms have still not been fully explained. This study investigated whether the treatment by digoxin contributes to mid– and long–term stabilization of ventricular cycles in patients with paroxysmal AF. A population of 45 patients with paroxysmal AF underwent 24–hour ECG recordings during each arm of a randomized crossover trial comparing digoxin and placebo. This yielded 30 Holter recordings from 22 patients that contained AF episodes lasting in excess of 2 minutes and with acceptably low Holter noise. Each AF episode was divided into nonoverlapping segments of 30 seconds and the distribution of RR intervals in each segment was compared with the distribution of all other AF segments in the same recording using the Kolmogorov–Smimov test. The percentage of tests that revealed significant differences at levels of P ≤ 0.01, and P ≤ 0.001 were sorted according to the time between the segments compared. The comparisons of these results were performed between: (a) all recordings on placebo (n = 16) and all recordings on digoxin (n = 14), and (b) between recordings on placebo and on digoxin in 8 patients in whom paired analysis was possible. Adjacent AF segments (distance 0) differed significantly only in < 30% of both recordings on placebo and on digoxin. However, with increasing the distance between segments, the proportion of the significant differences between RR interval distributions increased more with placebo than with digoxin (P < 10−300, Chi-square test). Paired data revealed larger differences between placebo and digoxin with increasing distance between segments. Thus in patients with paroxysmal AF, digoxin leads to more reproducible patterns of ventricular cycles that may be better tolerated clinically.
    Pacing and Clinical Electrophysiology 06/2006; 21(9):1735 - 1740. · 1.75 Impact Factor
  • John M Power, Jai Raman, Melissa J Byrne, Clif A Alferness
    [Show abstract] [Hide abstract]
    ABSTRACT: To utilise an ovine model of tachycardia induced progressive dilated cardiomyopathy and heart failure to investigate the efficacy of passive ventricular constraint with the Acorn cardiac support device as a heart failure treatment. (a) Moderate heart failure was produced in 16 sheep by pacing for 3 weeks. Half were implanted and half sham implanted with the CSD. Pacing continued at a higher rate for an additional 3 weeks. Cardiac function was assessed by echocardiography and manometry. (b) Moderate heart failure was produced (as above) in 27 sheep, 9 were implanted with CSD, pacing was restarted for 4 weeks, the initial CSD implants were terminated and another 9 animals were CSD implanted (severe heart failure), pacing was restarted in the remaining 18 animals for an additional 4 weeks (total 12 weeks) and then all animals were terminated. Cardiac function was assessed using echocardiography and treadmill exercise testing. (a) After 6 weeks of rapid pacing CSD implant animals had significantly better cardiac function both when compared with pre implant values and with non-implanted animals at termination. (b) CSD implantation at both moderate and severe failure resulted in significant improvements in cardiac function both when compared with pre implant values and with non-implanted animals at termination. When compared to pre implant values the improvement was greatest in severe implant animals. In this ovine model of tachycardia induced progressive heart failure, CSD implantation in either moderate or severe heart failure resulted in improved cardiac function, reduced left ventricular volume and mitral regurgitation both when compared with function at time of implant and with non implanted control animals.
    Heart Failure Reviews 07/2005; 10(2):117-23. · 4.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Functional mitral valve regurgitation plays a key role in the symptomatic severity and progression of heart failure. In an ovine model of dilated cardiomyopathy, we examined the chronic functional consequences of mitral regurgitation reduction using a recently developed novel percutaneous mitral annular reduction (PMAR) device. Fourteen adult sheep were paced right ventricularly at 180 to 190 bpm for 5 weeks, leading to the development of moderate mitral valve regurgitation. After echocardiographic, hemodynamic, and neurohormonal analysis, 9 animals underwent PMAR. All animals were subsequently paced for another 28 days, and a final echocardiographic and hemodynamic study was conducted. Animals that had undergone PMAR showed significantly increased negative and positive dP/dt, whereas pulmonary capillary wedge pressure and mitral valve regurgitation were significantly reduced compared with those at device implant despite continued pacing. In conjunction, significant improvements in plasma norepinephrine and brain natriuretic peptide were apparent. The application of PMAR in animals with pacing-induced dilated cardiomyopathy and functional mitral valve regurgitation resulted in continued improvements in hemodynamic and neurohormonal parameters.
    Circulation 12/2004; 110(19):3088-92. · 15.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mitral regurgitation (MR) frequently accompanies congestive heart failure (CHF) and is associated with poorer prognosis and more significantly impaired symptomatic status. Although surgical mitral valve annuloplasty has the potential to offer benefit, concerns about the combined surgical risk and possible effects on ventricular performance have limited progress. We evaluated the feasibility and short-term efficacy of a novel device placed in the coronary sinus to reduce MR in the setting of CHF. CHF and MR were induced in 9 adult sheep by rapid ventricular pacing for 5 to 8 weeks. A mitral annular constraint device was implanted percutaneously through the right internal jugular vein in the coronary sinus and great cardiac vein to create a short-term stable reduction (24.9+/-2.5%) in the mitral annular septal-lateral dimension as assessed echocardiographically. Right and left heart pressures and cardiac output were determined before and 15 minutes after device implantation. MR extent was examined echocardiographically and expressed as a ratio of left atrial area (MR/LAA). After device placement, MR was substantially reduced from an MR/LAA of 42+6% to 4+/-3% (P<0.01). In association, mean pulmonary wedge pressure was significantly reduced (26+/-3 to 18+/-3 mm Hg; P<0.01) and mean cardiac output significantly increased (3.4+/-0.3 to 4.3+/-0.4 L/min; P=0.01). In this model of CHF, percutaneous placement of a mitral annular constraint device in the coronary sinus resulted in the short-term elimination or minimization of MR and was accompanied in the short term by favorable hemodynamic effects.
    Circulation 10/2003; 108(15):1795-7. · 15.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We have shown that passive ventricular constraint during moderate heart failure can halt progressive deterioration in cardiac function in an experimental model of ovine pacing induced heart failure (HF). We report on ventricular constraint in severe heart failure. Eighteen adult merino sheep were used. Severe heart failure was induced in two stages, ie, high rate ventricular pacing for 21 days to produce moderate HF and then for 42 days to induce severe HF. A custom-made polyester mesh cardiac support device ([CSD] Acorn Cardiovascular, St Paul, MN) was implanted snugly around both ventricles through a lower partial sternotomy in 9 sheep (group 1). Rapid ventricular pacing was continued for a further 28 days in all animals to induce advanced HF. Cardiovascular functional indicators were determined using echocardiography and a submaximal treadmill exercise protocol at base line, moderate, severe, and advanced stages. The 9 sheep in group 2 were used as controls. Cardiovascular function was significantly depressed in all animals in advanced heart failure compared with base line, with left ventricular ejection fraction (LVEF) falling from 50% to 25% (p < 0.05) and LV +dp/dt((max)) declining from 1,777 to 1,243 (p < 0.05). However after CSD implantation cardiovascular function during exercise improved significantly despite ongoing rapid pacing, with LVEF increasing to 30% and LV +dp/dt to 1,499 (p < 0.05) in group 1. There were no significant changes in left ventricular long axis area (157 to 151 cm(2)) and short axis (6.8 to 6.1 cm) dimensions at the termination of pacing compared with those at time of CSD implant. Mitral regurgitation improved slightly from 2.5 to 2.19 after containment (p < 0.05) in group 1 but increased to 2.83 in group 2. Ventricular constraint in advanced heart failure with a custom-made polyester mesh device halted the decline in cardiac function seen in untreated animals with this pacing-induced animal model of heart failure. These results indicate potential clinical implications for ventricular containment in the treatment of end-stage heart failure.
    The Annals of Thoracic Surgery 08/2003; 76(1):141-7. · 3.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Heart failure (HF) is a progressive degenerative and malignant syndrome with a large number of aetiologies including coronary artery disease, chronic hypertension, exposure to toxins, bacteria and viruses and in a significant percentage of HF patients, the causal mechanism is unclear. The HF trail of morbidity and mortality is well documented and is characterised by step-like periods of relative symptomatic stability, compensation, separated by decompensatory episodes. The homeostatic response to the decline in cardiac function is diverse and involves most organs. There is an increase in resting rate, intra-cardiac hormone production (catecholamines, aldosterone, etc.) and in particular structural changes occur with increased mass and dilatation (dilated cardiomyopathy, DCM). DCM is associated with decreased cardiac output, contractility and energy efficiency and an increase in pro-arrhythmia and conduction defects. Kass et al. (Circulation 91(9) (1995) 2314) first demonstrated in patients who had undergone a dynamic cardio-myoplasty procedure, that, preventing further dilatation in DCM was beneficial and that the improved cardiovascular status was largely independent of muscle stimulation. We hypothesised that this outcome could be achieved by implanting a fabric cardiac support device around both ventricles to the AV junction. Subsequently, it was shown by us and others (Kass et al., 1995) (Cardiovasc. Res. 44(3) (1999) 549); (Ann. Thorac. Surg. 70(4) (2000) 1275) (in different animal models of DCM) that passive ventricular constraint prevented further dilatation, initiated left ventricular volume reduction and reversed the decline in ejection fraction, mitral valve integrity and left ventricular contractility, when compared with untreated controls. Subsequent European and North American clinical trials in patients with DCM of varying aetiologies have shown equal promise and an absence of device related complications (Circulation 104(12 Suppl. 1) (2001) I270); (Ann. Thorac. Cardiovasc. Surg. 7(5) (2001) 278). The mechanisms behind this improvement have yet to be fully clarified however the support generated by the device upon the right and ventricular freewall would lower wall tension. Not only is passive ventricular constraint a very promising treatment modality for heart failure and DCM it should provide a useful research tool for the study of the role of ventricular dilatation in the progression of heart failure.
    Progress in Biophysics and Molecular Biology 05/2003; 82(1-3):197-206. · 2.91 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to develop a model of long-term progressive heart failure (HF). A cardiac output flowprobe was implanted on the pulmonary artery of 9 adult sheep weighing 40 to 50 kg. Rapid ventricular pacing for 21 days at 160 to 190 bpm (rate A) resulted in moderate HF. Animals were then paced at 205 to 215 bpm (rate B) for 42 days (severe HF) and for 28 days at rate B (advanced HF). Data were collected at baseline and moderate, severe, and advanced HF during submaximal exercise testing and by transthoracic echocardiography in sinus rhythm. There were marked increases in left ventricular (LV) area, mitral valve regurgitation, and LV end-diastolic pressure and decreases in LV wall thickness, LV ejection fraction, positive and negative dP/dt(max), and positive (dP/dt(max))/P throughout the pacing protocol. This ovine HF model incorporates the progressive nature of human HF and allows examination of both structural changes and hemodynamic parameters of HF during and after exercise challenge.
    Journal of Cardiac Failure 05/2002; 8(2):108-15. · 3.32 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The acorn cardiac support device (ACSD) is a device designed to treat heart failure by containing the heart to prevent further dilation. Six patients with symptomatic heart failure due to ischemic cardiomyopathy were treated surgically with ACSD. All patients simultaneously underwent coronary artery bypass grafting. Ventricular reconstruction was also performed in 5 of the 6 patients. We followed up the patients for 12 months postoperatively, monitoring the left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), mitral regurgitation, and NYHA classification. Both the LVEDD and LVESD were significantly improved one month postoperatively (from 63.2 to 50.6 mm, p=0.004, and from 51.6 to 39.5 mm, p=0.025, respectively). These dimensions did not change significantly over the next 11 months. NYHA functional class improved significantly from a mean of 3 to 1.4 at 12 months (p=0.012). Mitral regurgitation improved from a mean of 2.7 preoperatively to 1.4 at 12 months and the average LVEF also improved from 27% preoperatively to 35.9% at 12 months after surgery. However these latter two results were not statistically significant. There were no late deaths and no readmissions for heart failure. Repeat coronary angiography at 6 months revealed patent grafts in all patients. The mid-term results of ACSD for patients with symptomatic heart failure suggest that ventricular containment may be useful for preventing further cardiac dilation in patients with ischemic cardiomyopathy. Randomized, long-term studies are needed to assess the efficacy and possible role of ASCD in the future management of heart failure.
    Annals of thoracic and cardiovascular surgery: official journal of the Association of Thoracic and Cardiovascular Surgeons of Asia 11/2001; 7(5):278-81. · 0.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Unsuccessful defibrillation shocks may reinitiate fibrillation by causing postshock reentry. To better understand why some waveforms are more efficacious for defibrillation, reentry was induced in six dogs with 1-, 2-, 4-, 8-, and 16-msec monophasic and 1/1- (both phases 1 msec) 2/2-, 4/4-, and 8/8-msec biphasic shocks. Reentry was initiated by 141+/-15 V shocks delivered from a defibrillator with a 150-microF capacitance during the vulnerable period of paced rhythm (183+/-12 msec after the last pacing stimulus). The shock potential gradient field was orthogonal to the dispersion of refractoriness. Activation was mapped with 121 electrodes covering 4 x 4 cm of the right ventricular epicardium, and potential gradient and degree of recovery of excitability were estimated at the sites of reentry. Defibrillation thresholds (DFTs) were estimated by an up-down protocol for the same nine waveforms in eight dogs internally and in nine other dogs externally. DFT voltages for the different waveforms were positively correlated with the magnitude of shock potential gradient and negatively correlated with the recovery interval at the site at which reentry was induced by the waveform during paced rhythm for both internal (DFT = 1719 + 64.5VV - 11.1RI; R2 = 0.93) and external defibrillation (DFT = 3445 + 150VV - 22RI; R2 = 0.93). The defibrillation waveforms with the lowest DFTs were those that induced reentry at sites of low shock potential gradient, indicating efficacious stimulation of myocardium. Additionally, the site of reentry induced by waveforms with the lowest DFTs was in myocardium that was more highly recovered just before the shock, perhaps because this high degree of recovery seldom occurs during defibrillation due to the rapid activation rate during fibrillation.
    Journal of Cardiovascular Electrophysiology 06/2001; 12(5):581-91. · 3.48 Impact Factor
  • Heart Lung &amp Circulation 12/2000; 9(3). · 1.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We examined the effects of passive containment of the cardiac ventricles with a surgically placed epicardial prosthetic wrap on indexes of left ventricular (LV) remodeling in dogs with heart failure. Heart failure (LV ejection fraction 30% to 40%) was produced in 12 dogs by intracoronary microembolization. Six dogs underwent mid-sternotomy and pericardiotomy with placement of a preformed-knitted polyester device (Acorn Cardiac Support Device [CSD], Acorn Cardiovascular, Inc, St. Paul, MN) snugly around the ventricles and anchored to the atrioventricular groove. Six dogs did not undergo surgery and served as controls. Dogs were followed for 3 months prior to sacrifice. In controls, LV end-diastolic volume increased after 3 months (67 +/- 12 versus 83 +/- 8 ml; p = 0.04), while in CSD-treated dogs, it decreased (68 +/- 10 versus 61 +/- 10 ml; p = 0.002). CSD-containment of LV size was associated with increased LV systolic fractional area of shortening, while in controls, fractional area of shortening decreased. CSD-treated dogs also showed amelioration of myocyte hypertrophy and attenuation of interstitial fibrosis compared to controls. In dogs with heart failure, passive epicardial containment of the ventricles with the Acorn CSD ameliorates LV remodeling and improves LV systolic function.
    The Annals of Thoracic Surgery 11/2000; 70(4):1275-80. · 3.45 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ventricular containment with custom-made polyester mesh is an evolving technique that has been studied in experimental animals with heart failure with good results. Five patients with symptomatic heart failure and ischemic cardiomyopathy were enrolled in a Phase I study, and underwent ventricular containment with custom-made polyester mesh along with coronary artery bypass grafting. Four patients had additional ventricular reconstruction of large myocardial scars. All patients were in NYHA functional class III at the time of their operation with a mean ejection fraction of 27.4%+/-6.6%. There were no deaths. Mean postoperative ejection fraction was 35.1%+/-12.6% (p = 0.16). Left ventricular end-diastolic diameter fell from 63.2+/-1.6 mm preoperatively to 50.6+/-5 mm, postoperatively (p = 0.004). There was no evidence of diastolic dysfunction or pericardial constriction on intra- or postoperative echocardiography. At a mean follow-up of 180 days all patients were in NYHA class I with no readmissions for heart failure. Repeat coronary angiography at 6 months revealed patent grafts in all patients. Ventricular containment with a customized mesh may be performed safely as an adjunct to conventional cardiac operation in patients with symptomatic heart failure. Longer follow-up with an expansion of the study will help delineate the long-term effects of this therapy.
    The Annals of Thoracic Surgery 10/2000; 70(3):1124-6. · 3.45 Impact Factor
  • J. Power, J. Raman, M. Byrne, C.A. Alferness
    European Journal of Heart Failure 06/2000; 2. · 5.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Dilated cardiomyopathy (DCM) is associated with a progressive deterioration in cardiac function. We hypothesised that some of the deleterious effects of DCM could be reduced by mechanically limiting the degree of cardiac dilatation. A Transonic 20A cardiac output (CO) flow-probe was implanted in the pulmonary artery of 12 adult (52 +/- 4 kg) sheep. Early heart failure was created by rapid right ventricular (RV) pacing for 21 days at a rate which resulted in an initial 10% decrease in CO (to a maximum of 190 bpm). A custom polyester jacket (Acorn Cardiovascular, St Paul, MN) was then placed, via a partial lower sternotomy, on the ventricular epicardium of all sheep. Animals were randomised either to jacket retention (wrap) or removal (sham). Pacing was recommenced at a higher rate (that initiated a further 10% decrease in CO) for 28 days. Haemodynamic and echocardiographic parameters were determined at baseline, implant and at termination. At termination, the left ventricular fractional shortening was significantly higher (p = 0.03), the degree of mitral valve regurgitation lower (scaled 0-3) (p = 0.03) and the left ventricular long axis area smaller (p = 0.02) in the wrap animals compared with sham. In this model of heart failure, ventricular constraint with a polyester jacket diminished the deterioration in cardiac function associated with progressive dilated cardiomyopathy. These results suggest that maintainance of a more normal cardiac size and shape may be beneficial in patients with dilated cardiomyopathy.
    Cardiovascular Research 01/2000; 44(3):549-55. · 5.81 Impact Factor
  • J. Raman, J. Power, B. Buxton, C. Alferness
    The Asia Pacific Heart Journal 01/1999; 8(1):63-64.
  • Journal of Cardiac Failure - J CARD FAIL. 01/1999; 5(3):32-32.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of digoxin on ventricular response during atrial fibrillation (AF) and consequent effects on arrhythmic symptoms have still not been fully explained. This study investigated whether the treatment by digoxin contributes to mid- and long-term stabilization of ventricular cycles in patients with paroxysmal AF. A population of 45 patients with paroxysmal AF underwent 24-hour ECG recordings during each arm of a randomized crossover trial comparing digoxin and placebo. This yielded 30 Holter recordings from 22 patients that contained AF episodes lasting in excess of 2 minutes and with acceptably low Holter noise. Each AF episode was divided into nonoverlapping segments of 30 seconds and the distribution of RR intervals in each segment was compared with the distribution of all other AF segments in the same recording using the Kolmogorov-Smirnov test. The percentage of tests that revealed significant differences at levels of P < or = 0.01, and P < or = 0.001 were sorted according to the time between the segments compared. The comparisons of these results were performed between: (a) all recordings on placebo (n = 16) and all recordings on digoxin (n = 14), and (b) between recordings on placebo and on digoxin in 8 patients in whom paired analysis was possible. Adjacent AF segments (distance 0) differed significantly only in < 30% of both recordings on placebo and on digoxin. However, with increasing the distance between segments, the proportion of the significant differences between RR interval distributions increased more with placebo than with digoxin (P < 10(-300), Chi-square test). Paired data revealed larger differences between placebo and digoxin with increasing distance between segments. Thus in patients with paroxysmal AF, digoxin leads to more reproducible patterns of ventricular cycles that may be better tolerated clinically.
    Pacing and Clinical Electrophysiology 10/1998; 21(9):1735-40. · 1.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Left atrial (LA) dilation is a common finding in patients with chronic atrial fibrillation (AF). Progressive dilatation may alter the atrial defibrillation threshold (ADFT). In our study, epicardial electrodes were implanted on the LA free wall and right ventricular apex of eight adult sheep. Large surface area, coiled endocardial electrodes were positioned in the coronary sinus and right atrium (RA). LA dilatation was induced by rapid ventricular pacing (190 beats/min) for 6 weeks and echocardiographically assessed weekly along with the ADFT (under propofol anesthesia). LA effective refractory period (ERP) was measured every 2-3 days using a standard extra stimulus technique and 400 ms drive. The AF cycle length (AFCL) was assessed from LA electrograms. During the 6 weeks of pacing the mean LA area increased from 6.1 +/- 1.5 to 21.3 +/- 2.4 cm2. There were no significant changes in the mean ADFT (122 +/- 15 V), circuit impedance (46 +/- 5 omega), or LA AFCL (136 +/- 23 ms). There was a significant increase in the mean LA ERP (106 +/- 10 ms at day 0, and 120 +/- 13 ms at day 42 of pacing). In this study, using chronically implanted defibrillation leads, the minimal energy requirements for successful AF were not significantly altered by ongoing left atrial dilatation. This finding is a further endorsement of the efficiency of the coronary sinus/RA shock vector. Furthermore, the apparent stability of the AF present may be a further indication of a link between the type of AF and the ADFT.
    Pacing and Clinical Electrophysiology 09/1998; 21(8):1595-600. · 1.75 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the defibrillator waiting time (time between the recognition of atrial fibrillation and the actual shock) by studying paroxysmal atrial fibrillation episodes with RR intervals shorter than a certain limit (that is, episodes during which defibrillation should not be attempted). Long term 24 hour Holter recordings from a digoxin v placebo crossover study in patients with paroxysmal atrial fibrillation were analysed. In all, 23 recordings with atrial fibrillation episodes of at least 1000 ventricular cycles and with < 20% Holter artefacts or noise were used (11 recorded on placebo and 12 on digoxin). For each recording, the mean ("mean waiting time") and maximum ("maximum waiting time") duration of continuous sections of atrial fibrillation episodes with all RR intervals shorter than a certain threshold were evaluated, ranging the threshold from 400 to 1000 ms in 10 ms steps. For each threshold, the mean and maximum waiting times were compared between recordings on placebo and on digoxin. Both the mean and maximum waiting times increased exponentially with increasing threshold. Practically acceptable mean waiting times less than one minute were observed with thresholds below 600 ms. There were no significant differences in mean waiting times and maximum waiting times between recordings on placebo and digoxin, and only a trend towards shorter waiting times on digoxin. Introduction of a minimum RR interval threshold required to deliver atrial defibrillation leads to practically acceptable delays between atrial fibrillation recognition and the actual shock. These delays are not prolonged by digoxin treatment.
    Heart (British Cardiac Society) 05/1998; 79(5):497-501. · 5.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing-induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters. Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF threshold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6-week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA ERP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology. In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.
    Journal of Cardiovascular Electrophysiology 04/1998; 9(4):423-35. · 3.48 Impact Factor

Publication Stats

759 Citations
157.15 Total Impact Points

Institutions

  • 2005
    • Baker IDI Heart and Diabetes Institute
      Melbourne, Victoria, Australia
  • 2003
    • University of Chicago
      Chicago, Illinois, United States
  • 2001
    • University of Alabama at Birmingham
      • Department of Medicine
      Birmingham, AL, United States
  • 1995–1998
    • St. George's School
      • Department of Cardiological Sciences
      Middletown, Rhode Island, United States
  • 1991–1994
    • Duke University
      • Department of Biomedical Engineering (BME)
      Durham, North Carolina, United States
  • 1990–1994
    • Duke University Medical Center
      • Department of Medicine
      Durham, NC, United States
    • Rose Hulman Institute of Technology
      Indiana, United States