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the converse is overdiagnosis of ventricular tachycardia
- oscar,m jolobe (29 October 2008)
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Misdiagnosis of ventricular tachycardia
- David E Ward (14 November 2008)
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Slow Ventricular tachycardia is an under-recognised cause of symptomatic deterioration in heart failure patients
- Nicolas Gall, Dr John Rawlins, Dr Shaumik Adhya (5 March 2009)
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oscar,m jolobe, retired geriatrician manchester medical society, c/o john rylands university library, oxford road, manchester M13 9PP
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Although independent atrial activity and, hence, atrio-ventricular dissociation(A-V dissociation) is recognised as being fundamental to the diagnosis of ventricular tachycardia(VT)(1), there are exceptions to this rule(2), and one of them is co-existing atrial fibrillation(AF)(2), exemplified by the simltaneous documentation of atrial complexes typical of AF in one of 70 patients with validated VT(2). Ventricular tachycardia has also been documented in a patient with myocardial infarction who presented with haemodynamically stable AF, and in whom paroxysms of VT gave rise to subsequent deterioration in haemodynamic status(3). Conversely, in irregular tachycardia with wide QRS complexes "differential diagnosis will be among...atrial fibrillation with aberrant condunduction...and...irregular ventricular tachycardia"(2). Irregularity of VT, in the latter study, occured in 13 instances, and this was not only in the presence of capture beats(four instances), but also in the presence of uniform QRS morphology(nine instances)(2). Atrial fibrillation is most likely to simulate VT when the ventricular rate is rapid(for example > 160 beats/minute) because irregularity of the ventricular response is less obvious when the ventricular rate is rapid(4). This was the most likely reason why, in that study, three ot of 100 house officers mistook fast AF(with ventricular rate 162/minute) for VT(4). Accordingly, the differential diagnosis between VT and supraventricular tachyarrythmias can be difficult when independent atrial activity is not easily identifiale, and this difficulty is compounded by the fact that A-V dissociation in identifiable only in the minority of cases, and this applies to VT with broad QRS morphology(2), and also to VT with narrow QRS complexes(5). References (1) Leitz N., Khawaja Z., Been M Slow ventricular tachycardia British medical Journal 2008:337:a424 (2) Wellens HJJ., Bart FWH., Lie KI The value of the electrocardiogram in the differential diagnosis of a tachycardia with widened QRS complex American Journal of Medicine 1978:64:27-33 (3) Ramsdale DR., Peterson C Succesful termination of combined rapid atrial flutter/fibrillation and ventricular tachycardia by intravenous sotalol Postgraduate Medical Journal 1987:63:579-80 (4) Knight BP., Zivin A., Souza J et al Use of adenosine in patients hospitalised in a university medical center American Journal of Medicine 1998:105:275-280 (5)Hayes JJ., Stewardt RB., Greene L., Bardy GH Narrow QRS ventricular tachcardia Annals of Internal Medicine 1991:114:460-3 Competing interests: None declared |
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David E Ward, Consultant Cardiologist St George's Hospital, London, SW17 0QT
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The case reports by Leitz et al are timely and their points are well made. This very problem was reviewed in 1985 by Dancy et al (Lancet 1985; ii; 320-23). One of the most serious consequences of misdiagnosis is inappropriate therapy. This applies especially to intravenous verapamil (appropriate for SVT) which is a cardiac depressant. The consequent hypotension may be a prelude to cardiac arrest and death. The default diagnosis for wide complex tachycardia of any rate, whether slow or fast should therefore be "ventricular tachycardia". Over diagnosis of VT in an acute situation is not deleterious. All patients should subsequently be reviewed by an electrophysiologist who should ensure that correct investigation and treatment is instigated. Competing interests: None declared |
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Nicolas Gall, Consultant Cardiologist Kings College Hospital, SE5 9RS, Dr John Rawlins, Dr Shaumik Adhya
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Leitz et al (1) highlight the importance of recognising slow ventricular tachycardia (VT). Therapy in heart failure with implanted devices is becoming increasingly frequent and complex with recent advances allowing remote monitoring of patients. We present a case of slow ventricular tachycardia which was diagnosed early due to an implanted device. Implantable device therapy in heart failure is increasingly indicated especially in response to recent NICE guidance (2,3). There are two primary indications for device therapy in heart failure patients. Firstly, in many patients with clinical heart failure, objective evidence of severe systolic dysfunction and a broad QRS complex on the ECG, the heart is thought to contract dyssynchronously. Cardiac resynchronisation therapy (CRT) utilises a pacemaker with leads able to pace both right and left ventricles in order to resynchronise cardiac contraction. Evidence suggests that this leads to significant improvements to symptoms and reduced mortality(4). Secondly, many patients with heart failure, have an increased risk of sudden cardiac death, and may therefore be a candidate for the prophylactic implantation of a cardioverter-defibrillator (ICD) which can treat ventricular arrhythmias. Both situations often co-exist, and devices are available which combine both functions, termed CRT-D. Modern CRT-D devices may incorporate functions allowing patients to monitor their condition at home. A handheld monitor can give audio-visual alarms to alert the patient to problems. Patients are also able to download information stored by the device, and using a standard phone line, transfer this information to a remote site, for example a hospital or clinic. These algorithms may provide a sub-clinical marker of deterioration, prompting earlier intervention, by either the patient or via advice from a health practitioner and may avoid hospital admission. The OptiVol™ system is one of these methods. It passes an electrical current across the thorax, between the distal end of the pacing lead and the device box. An increase in intra-thoracic fluid, as occurs in pulmonary oedema, causes a decrease in the resistance to current flow (impedance) which can trigger an alarm. The MIDHEFT study (5) suggested that the use of the OptiVol™ device could identify early deterioration in patients and reduce the frequency of hospital admission. The investigators observed a decrease in impedance and the triggering of an OptiVol™ alert preceded the development of symptoms by 15 days. This is being further investigated in a prospective multi- centre trial – termed DOT-HF. We present the case of an 82 year old lady with a history of myocardial infarction and NYHA class III heart failure on optimal medical therapy who had a CRT-D (Medtronic Consulta™) implanted in 2008. She presented several months later because she had heard an audible alarm from her device following an episode of severe diahorrea. Interrogation of her CRT-D revealed a 36 hour long episode of sustained VT with a rate of 140 beats per minute (bpm). The CRT-D had recognised the tachycardia, but because it was below any therapy threshold, it had not initiated any treatment. Slow ventricular tachycardia was triggered as a result of the electrolyte disturbance induced by the diahorrea. The VT had adversely affected her cardiac output resulting in an increase in lung fluid levels, which had triggered the OptiVol™ device to alarm and led to her seeking medical advice. The rate of the VT was slow enough so that she remained essentially asymptomatic of its occurrence although it seems likely that she would have eventually presented with pulmonary oedema some days later. She was treated with the addition of Amiodarone to her maximal â- blocker therapy. Her device was re-programmed to recognise slow VT and to deliver anti-tachycardia pacing. Shock therapy was reserved for faster ventricular arrhythmias. She was not admitted to hospital. The addition of amidoarone has thus far prevented further episodes of VT and associated breathlessness This case illustrates the benefits of remote monitoring with implantable devices to improve patient care and allow timely intervention for conditions such as ventricular tachycardia. Devices such as this will become increasingly commonplace and clinicians should be aware of their uses and potential benefits. We believe this is the first reported case of an implanted system with an audible alarm prompting the recognition of slow VT. Dr John Rawlins BSc (Hons) MRCP
1. N. Leitz, Z. Khawaja, and M. Been Slow ventricular tachycardia BMJ, July 3, 2008; 337(jul03_1): a424 - a424 2. http://www.nice.org.uk/guidance/TA120, 3. http://www.nice.org.uk/TA095 4. John G.F. Cleland, M.D., Jean-Claude Daubert, M.D., Erland Erdmann, M.D., Nick Freemantle, Ph.D., Daniel Gras, M.D., Lukas Kappenberger, M.D., Luigi Tavazzi, M.D., for the Cardiac Resynchronization — Heart Failure (CARE-HF) Study InvestigatorsThe Effect of Cardiac Resynchronization on Morbidity and Mortality in Heart Failure N Engl J Med 2005; 353:205-206, Jul 14, 2005 5. Yu, Cheuk-Man MD, FRCP; Wang, Li PhD; Chau, Elaine FRCP; Chan, Raymond Hon-Wah FRCP; Kong, Shun-Ling BN; Tang, Man-Oi BM; Christensen, Jill PhD; Stadler, Robert W. PhD; Lau, Chu-Pak MD, FRCP Intrathoracic Impedance Monitoring in Patients With Heart Failure: Correlation With Fluid Status and Feasibility of Early Warning Preceding Hospitalization. Circulation:Volume 112(6)9 August 2005pp 841-848 Competing interests: Competing Interests – Author (S.A.) holds a research fellowship funded by Medtronic. DR N Gall has received honoraria from Medtronic, Bostons Scientific, St Jude Medical and Sorin ELA. Editorial note
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