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BMJ (Clinical research ed.). 05/2008; 336(7648):830-2.
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ABSTRACT: The complications and limitations of biventricular pacing largely relate to left ventricular (LV) pacing. An alternative approach was tested of simultaneously pacing the right ventricular (RV) apex and outflow tract (RVOT) or using bifocal right ventricular pacing (BRVP) to provide cardiac resynchronisation.
21 consecutive patients with heart failure and severely impaired left ventricular function were studied. Ejection fraction and tissue Doppler data were collected at baseline, during BRVP, and during biventricular pacing, using a temporary pacing protocol.
BRVP was achieved in all patients without complication. BRVP significantly reduced mean baseline intra-LV, inter-LV-RV, and global mechanical dyssynchrony from (mean (SD)) 71 (35) to 44 (18) ms, p = 0.003; 86 (42) to 57 (33) ms, p = 0.029; and 157 (67) to 101 (42) ms, p = 0.005, respectively. It increased the ejection fraction from 21 (8)% to 29 (7)%, p = 0.002. Compared with BRVP, reductions in intra-LV, inter-LV-RV, and global mechanical dyssynchrony were superior with biventricular pacing (31 (12) ms, p = 0.014; 36 (27) ms, p = 0.008; and 67 (34) ms, p = 0.01 compared with BRVP, respectively); improvements in ejection fraction were similar (26 (9)%, NS).
In patients with heart failure, superior mechanical resynchronisation is achieved with biventricular pacing compared with BRVP. BRVP may be useful when left ventricular lead placement is not possible.
Heart (British Cardiac Society) 02/2008; 94(1):53-8. · 4.22 Impact Factor
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ABSTRACT: To determine the effects of interventricular pacing interval and left ventricular (LV) pacing site on ventricular dyssynchrony and function at baseline and during biventricular pacing, using tissue Doppler imaging.
Using an angioplasty wire to pace the left ventricle, 20 patients with heart failure and left bundle branch block underwent temporary biventricular pacing from lateral (n = 20) and inferior (n = 10) LV sites at five interventricular pacing intervals: +80, +40, synchronous, -40, and -80 ms.
LV ejection fraction (EF) increased (mean (SD) from 18 (8)% to 26 (10)% (p = 0.016) and global mechanical dyssynchrony decreased from 187 (91) ms to 97 (63) ms (p = 0.0004) with synchronous biventricular pacing compared to unpaced baseline. Sequential pacing with LV preactivation produced incremental improvements in EF and global mechanical dyssynchrony (p<0.0001 and p = 0.0026, respectively), primarily as a result of reductions in inter-LV-RV dyssynchrony (p = 0.0001) rather than intra-LV dyssynchrony (NS). Results of biventricular pacing from an inferior or lateral LV site were comparable (for example, synchronous biventricular pacing, global mechanical dyssynchrony: lateral LV site, 97 (63) ms; inferior LV site, 104 (41) ms (NS); EF: lateral LV site, 26 (10)%; inferior LV site, 27 (10)% (NS)). ECG morphology was identical during biventricular pacing through an angioplasty wire and a permanent lead.
Sequential biventricular pacing with LV preactivation most often optimises LV synchrony and EF. An inferior LV site offers a good alternative to a lateral site. Pacing through an angioplasty wire may be useful in assessing the acute effects of pacing.
Heart (British Cardiac Society) 11/2007; 93(11):1426-32. · 4.22 Impact Factor
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ABSTRACT: Atrial flutter is a common arrhythmia. In the critical care setting, the arrhythmia may present in any patient, but it is most commonly seen in patients with impaired ventricular function, valvular disease, atrial dilatation or after cardiac surgery. We present a 68-year-old lady with recurrent poorly tolerated atrial flutter that was resistant to multiple pharmacological interventions and complicated by cardiogenic shock following direct current cardioversion. The flutter was successfully cured with radiofrequency ablation and was followed by an immediate improvement in her haemodynamic status. We review the management of acute atrial flutter and discuss the role of electrophysiologically guided ablation.
Anaesthesia 06/2005; 60(5):505-8. · 2.96 Impact Factor
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ABSTRACT: To investigate whether a rapid access approach is useful for the evaluation of patients with symptoms suggestive of a new cardiac arrhythmia.
Prospective, descriptive study.
Secondary care based rapid access arrhythmia clinic in West London, UK.
Patients referred by their general practitioner or the emergency department with symptoms suggestive of a new cardiac arrhythmia.
Number of patients with a newly diagnosed significant arrhythmia. Number of patients with diagnosed atrial fibrillation. Number of eligible, moderate, and high risk patients treated with warfarin.
Over a 25 month period 984 referrals were assessed. The mean age was 55 years (range 20-90 years) and 56% were women. The median time from referral to assessment was one day. A significant cardiac arrhythmia was newly diagnosed in 40% of patients referred to the RAAC. The most common arrhythmia was atrial fibrillation, with 203 new cases (21%). Of these, 74% of eligible patients over 65 were treated with warfarin. Other arrhythmias diagnosed were supraventricular tachycardias (127 (13%)), conduction disorders (43 (4%)), and non-sustained ventricular tachycardia (21 (2%)). Vasovagal syncope was diagnosed for 53 patients (5%). The most frequent diagnosis was symptomatic ventricular and supraventricular extrasystoles (355 (36%)).
A rapid access arrhythmia clinic is an innovative approach to the diagnosis and management of new cardiac arrhythmias in the community. It provides a rapid diagnosis, stratifies risk, and leads to prompt initiation of effective treatment for this population.
Heart (British Cardiac Society) 09/2004; 90(8):877-81. · 4.22 Impact Factor
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ABSTRACT: Intermittent pneumatic compression (IPC) may increase blood flow through infrainguinal arterial grafts, and has potential clinical application as blood flow velocity attenuation often precedes graft failure. The present study examined the immediate effects of IPC applied to the foot (IPC(foot)), the calf (IPC(calf)) and to both simultaneously (IPC(foot+calf)) on the haemodynamics of infrainguinal bypass grafts.
Eighteen femoropopliteal and 18 femorodistal autologous vein grafts were studied; all had a resting ankle : brachial pressure index of 0.9 or more. Clinical examination, graft surveillance and measurement of graft haemodynamics were conducted at rest and within 5 s of IPC in each mode using duplex imaging. Outcome measures included peak systolic (PSV), mean (MV) and end diastolic (EDV) velocities, pulsatility index (PI) and volume flow in the graft.
All IPC modes significantly enhanced MV, PSV, EDV and volume flow in both graft types; IPC(foot+calf) was the most effective. IPC(foot+calf) enhanced median volume flow, MV and PSV in femoropopliteal grafts by 182, 236 and 49 per cent, respectively, and attenuated PI by 61 per cent. Enhancement in femorodistal grafts was 273, 179 and 53 per cent respectively, and PI attenuation was 63 per cent.
IPC was effective in improving infrainguinal graft flow velocity, probably by reducing peripheral resistance. IPC has the potential to reduce the risk of bypass graft thrombosis.
British Journal of Surgery 05/2004; 91(4):429-34. · 4.61 Impact Factor
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ABSTRACT: This study was done to characterize human right atrial (RA) flutter (AFL) using noncontact mapping.
Atrial flutter has been mapped using sequential techniques, but complex anatomy makes simultaneous global RA mapping difficult.
Noncontact mapping was used to map the RA of 13 patients with AFL (5 with previous attempts), 11 with counterclockwise and 2 with clockwise AFL. "Reconstructed" electrograms were validated against contact electrograms using cross-correlation. The Cartesian coordinates of points on a virtual endocardium were used to calculate the length and thus the conduction velocity (CV) of the AFL wave front within the tricuspid annulus-inferior vena cave isthmus (IS) and either side of the crista terminalis (CT).
When clearly seen, the AFL wave front split (n = 3) or turned in the region of the coronary sinus os (n = 6). Activation progressed toward the tricuspid annulus (TA) from the surrounding RA in 10 patients, suggesting that the leading edge of the reentry wave front is not always at the TA. The IS length and CV was 47.73 +/- 24.40 mm (mean +/- SD) and 0.74 +/- 0.36 m/s. The CV was similar for the smooth and trabeculated RA (1.16 +/- 0.48 m/s and 1.22 +/- 0.65 m/s, respectively [p = 0.67]) and faster than the IS (p = 0.03 and p = 0.05 for smooth and trabeculated, respectively).
Noncontact mapping of AFL has been validated and has demonstrated that IS CV is significantly slower than either side of the CT.
Journal of the American College of Cardiology 09/2001; 38(2):385-93. · 14.16 Impact Factor
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Journal of Human Hypertension 09/2001; 15 Suppl 1:S95-6. · 2.80 Impact Factor
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ABSTRACT: Prolonged arrhythmic or paced ventricular activation causes persistent changes in myocardial conduction and repolarization that may result from altered electrotonic current flow, for which gap junctional coupling is the principal determinant. Remodeling of gap junctions and their constituent connexins modifies conduction and has been causally implicated in reentrant arrhythmogenesis. We hypothesized conversely that altering the pattern of ventricular activation causes gap junctional remodeling.
Seven dogs were paced from the left ventricular (LV) epicardium (VVO, approximately 120 beats/min) for 21 days before excision of transmural LV samples that were divided into endomyocardial, mid-myocardial, and epimyocardial layers. Another five paced dogs had recording electrodes attached to multiple LV sites. All 12 dogs developed characteristic pacing-induced persistent T wave changes of cardiac memory. After 21 days of pacing, the ventricularly paced QRS duration prolonged by a mean of 4 msec over baseline (P < 0.05), a change that was associated with significant slowing of intraventricular conduction to local sites. These changes in QRS duration and repolarization were associated with a reduction in epimyocardial connexin43 expression on quantitative Western blotting of LV myocardium from close to, but not distant from, the pacing site (61.7+/-18.4 vs 100.9+/-34.0; P < 0.02) and a marked disruption in immunolabeled connexin43 distribution in epimyocardium only.
Spatially distinct transmural and regional gap junctional remodeling is a consequence of abnormal ventricular activation and is associated with consistent changes in activation that may alter patterns of repolarization and facilitate reentrant arrhythmogenesis.
Journal of Cardiovascular Electrophysiology 05/2001; 12(5):570-7. · 3.06 Impact Factor
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ABSTRACT: Resetting has been used to characterize reentrant circuits causing clinical tachycardias.
To determine the mechanisms of resetting, sustained ventricular tachycardia was induced in dogs with 4-day-old myocardial infarctions by programmed stimulation. Premature stimulation was accomplished from multiple regions within reentrant circuits; resetting curves were constructed and compared with activation maps. Monotonically increasing responses, or a "mixed" response (increasing portion preceded by a flat portion), occurred. All reentrant circuits had a fully excitable gap. Interval-dependent conduction delay and concealed retrograde penetration led to increased resetting response curves.
Multiple mechanisms revealed by mapping cause resetting of reentrant circuits.
Circulation 03/2001; 103(8):1148-56. · 14.74 Impact Factor
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European Heart Journal 07/2000; 21(11):884-9. · 10.48 Impact Factor
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European Heart Journal 06/2000; 21(10):801-7. · 10.48 Impact Factor
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Journal of Cardiovascular Electrophysiology 05/2000; 11(4):488-90. · 3.06 Impact Factor
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ABSTRACT: Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy.
A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium. Patients had either sustained atrial fibrillation (n=3) for >6 months or developed atrial fibrillation during the study (n=8). Spontaneous initiation of atrial fibrillation was recorded in one patient and was demonstrated by the non-contact system to arise from two successive atrial ectopic beats from the site of a roving contact catheter. Reconstruction of electrograms recorded during atrial fibrillation was validated by comparison with contact electrograms with cross-correlation. During established atrial fibrillation, four patients predominantly had a single right atrial wave front, two had two wave fronts and five patients had three to five wave fronts for most of the time. Periods of electrical silence were seen in the right atrium in eight patients, after which, activity emerged from consistent septal sites alone, suggesting a left atrial origin. During intravenous administration of flecainide, atrial fibrillation in two patients terminated spontaneously or following pacing manoeuvres, while in the remaining patient sinus rhythm was restored via atrial tachycardia.
Non-contact mapping of the right atrium has demonstrated modes of initiation and termination of atrial fibrillation, characterized different patterns of right atrial activation in atrial fibrillation and suggests that the left atrium may sustain atrial fibrillation in some patients. Simultaneous mapping of the right and left atrium is required to further elucidate the mechanisms of human atrial fibrillation.
European Heart Journal 04/2000; 21(7):550-64. · 10.48 Impact Factor
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ABSTRACT: Focal left atrial (LA) tachycardias/ectopy (LATs) that may
initiate atrial fibrillation (AF) are often difficult to initiate,
non-sustained, and may have multiple origins, often in one or more
pulmonary veins (PV). Thus, mapping with conventional techniques is
often difficult. The authors tested the hypothesis that a non-contact
mapping system capable of global simultaneous mapping of >3000 points
in the LA, would facilitate ablation of LAT. The non-contact mapping
system was able to rapidly identify the origin of human LATs and focal
AF despite the infrequency and short duration of initiating ectopy and
guide a conventional mapping catheter to successful ablation sites. The
authors also observed that, although isoproterenol is the most
successful method of initiating LATs, these originate from multiple
sites and therefore appear to be of limited clinical significance
Computers in Cardiology 2000; 02/2000
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ABSTRACT: The pattern of left atrial (LA) activation during sinus rhythm
(SR) in humans has not been delineated. The authors used a non-contact
mapping system to analyze the patterns of left atrial (LA) activation
during sinus rhythm and pacing. The system is capable of simultaneously
reproducing more than 3,000 electrograms, which are superimposed on a
virtual left atrial endocardium. Data were recorded in sinus rhythm and
during pacing from the high right atrium, coronary sinus os, and right
atrial septum. The authors demonstrate that during sinus rhythm, the LA
activates mainly through posterior septal fibers, adjacent to the ostia
of the right pulmonary veins. This suggests that, in humans, anterior
interatrial connections including Bachmann's bundle may be less
important than previously recognized
Computers in Cardiology 2000; 02/2000
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ABSTRACT: The conduction characteristics of human ventricular tachycardias
(VT) have not been fully defined. The authors used a non-contact system
to map 11 reentrant VT in 8 patients. Propagation velocities and
3-dimensional angles of turn were calculated from Cartesian
co-ordinates. The complete diastolic pathway (DP) was mapped in 7 VT
patients. DP wavefront velocity was 0.82±0.49 m/s. Significant
changes (>5 degrees/mm) in trajectory of propagation (TOP) occurred
within 8 DP segments, in which propagation slowed to 0.41±0.11
m/s compared with 0.91±0.16 m/s preceding (p<0.05) and
1.07±0.33 following (p<0.05) change in TOP. At entry turning
points (TP) propagation velocity slowed from 1.3±0.4 ms to
0.6±0.26 ms (P<0.001), but did not change at exit TP on
leaving the distal DP (0.72±0.28 vs 0.8±0.25 m/s, p=ns).
In conclusion, slowing of propagation in human VT circuits occurs over
regions of wavefront turning
Computers in Cardiology 2000; 02/2000
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ABSTRACT: Treatment of ventricular tachycardia (VT) in coronary heart disease has to date been limited to palliative treatment with drugs or implantable defibrillators. The results of curative treatment with catheter ablation have proved disappointing because the complexity of the VT mechanism makes identification of the substrate using conventional mapping techniques difficult. The use of a mapping technology that may address some of these issues, and thus make possible a cure for VT with catheter ablation, is reported.
The non-contact system, consisting of a multielectrode array catheter (MEA) and a computer mapping system, was used to map VT in 24 patients. Twenty two patients had structural heart disease, the remainder having "normal" left ventricles with either fasicular tachycardia or left ventricular ectopic tachycardia.
Exit sites were demonstrated in 80 of 81 VT morphologies by the non-contact system, and complete VT circuits were traced in 17. In another 37 morphologies of VT 36 (30)% (mean (SD)) of the diastolic interval was identified. Thirty eight VT morphologies were ablated using 154 radiofrequency energy applications. Successful ablation was achieved by 77% of radiofrequency within diastolic activation identified by the non-contact system and was significantly more likely to ablate VT than radiofrequency at the VT exit, or remote from diastolic activation. Over a mean follow up of 1.5 years, 14 patients have had no recurrence of VT and only two target VTs have recurred. Five patients have had recurrence of either slower non-sustained, undocumented or fast non-target VT. Five patients have died, one from tamponade from a pre-existing temporary pacing wire, and four from causes unrelated to the procedure.
The non-contact system can safely be used to map and ablate haemodynamically stable VT with low VT recurrence rates. It is yet to be established whether this system may be applied with equal success to patients with haemodynamically unstable VT.
Heart (British Cardiac Society) 07/1999; 81(6):570-5. · 4.22 Impact Factor
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ABSTRACT: Catheter ablation of ventricular tachycardia (VT) is limited by difficulty in identifying suitable sites for ablation. This study assesses use of a system capable of simultaneous endocardial mapping of the human left ventricle to map and guide radiofrequency (RF) catheter ablation of VT.
A catheter-mounted noncontact multielectrode array was used to reconstruct 3360 electrograms, superimposed onto a computer-simulated endocardial model. Of 24 patients studied, 20 had ischemic heart disease. Exit sites were demonstrated by the noncontact system in 80 (99%) of 81 VTs, with complete VT circuits traced in 17 (21%). In another 37 VTs, 36+/-30% (mean+/-SD) of the diastolic interval was identified. Thirty-eight VT morphologies were ablated with 154 RF energy applications. Successful ablation was achieved by 77% of RF applications to relevant diastolic activity identified by the system and was significantly more likely (P<0.0001) than by RF at the VT exit or remote from diastolic activation. Over a mean follow-up of 1.5 years, 14 patients (64%) have had no recurrence of VT, and only 2 target VTs (5.3%) have recurred. Five patients have had recurrence of other VTs.
This noncontact mapping system identified diastolic portions of the circuit in most VTs studied and can safely map and guide ablation of human VT.
Circulation 05/1999; 99(19):2543-52. · 14.74 Impact Factor
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ABSTRACT: The development of new mapping systems is beginning to overcome some of the limitations of conventional techniques by offering percutaneous deployment, simultaneous acquisitions of data, high-resolution maps, and correlation of anatomy and electrophysiology, in addition to a catheter location system. The noncontact mapping system continues to undergo development and does not completely address all requirements for an ideal mapping system. The limitations of the system include deterioration in the quality of electrogram reconstruction with increasing distance between the MEA and the endocardium, the inability of the noncontact system to identify subendocardial activation, and problems with distinguishing noise from low-amplitude diastolic electrograms.
Journal of Electrocardiology 02/1999; 32 Suppl:13-5. · 1.14 Impact Factor
