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Jeremy Rowland is a senior house officer in old age psychiatry based at the Hesketh Centre (Merseycare NHS Trust, 5155 Albert Road, Southport, Merseyside PR9 0LT, UK. Email: jezrowland{at}yahoo.com). He moved into psychiatry after initially training in general medicine and gaining membership of the Royal College of Physicians. John Rigby is a consultant psychiatrist and clinical director of the Older Peoples Mental Health Services in Mersey Care NHS Trust. Adam Harper is a consultant geriatrician for Brighton and Sussex University Hospitals NHS Trust. Rosalind Rowland is a general physician currently studying at the Liverpool School of Tropical Medicine.
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The risk of significant and potentially serious cardiovascular side-effects of AChE inhibitors was highlighted from the outset, and product information stated that they have a vagotonic effect on the heart. Although product information for all three drugs gave low rates of cardiovascular adverse effects (Table 1
), sick sinus syndrome and cardiac conduction defects were quoted as relative contraindications to their use. The manufacturers of donepezil, rivastigmine and galantamine (under the trade names Aricept, Exelon and Reminyl respectively) also advised that the drugs should be used with caution in patients taking concurrent medications that reduce heart rate such as digoxin and beta-blockers. There thus followed some uncertainty as to how treatment should be properly managed.
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This article arose from the need to develop a simple approach to managing cardiovascular risk in patients with Alzheimers disease attending a memory clinic for the prescription of AChE inhibitors. In preparing appropriate guidelines we reviewed the incidence and severity of cardiovascular adverse events described in the original randomised controlled trials with donepezil, galantamine and rivastigmine, as well as subsequent open-label studies, and experience from case reports. We asked ourselves the following questions: does currently available evidence support the need for cardiovascular screening and monitoring when using AChE inhibitors? What screening tool should be used? Should screening apply to all patients receiving treatment, or just be targeted at high-risk groups?
| Therapeutic use of AChE inhibitors in Alzheimers disease |
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| Potential for cardiovascular adverse events |
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Parasympathetic activity dominates neural control of heart rate and cardiac function.1 Increased levels of acetylcholine stimulate GABAergic and glycinergic inhibitory receptors by triggering vagal neurotransmission (Wang et al, 2003), and this vagal activity, via muscarinic receptors, acts to slow heart rate. Therefore, theoretically, AChE inhibitors can induce sinus bradycardia, sino-atrial block, and aggravate pre-existing sinus node disease and atrioventricular block (Savie et al, 1998) (Box 1
). In support of this theory, donepezil overdose has been reported to result in profound sinus bradycardia that can be reversed with atropine (Shepherd et al, 1999; Hidetaka et al, 2003). Furthermore, edrophonium, an anti-cholinesterase, has been shown to have a strong ability to induce syncope during head-up tilt-testing (Fitzpatrick et al, 1996). Finally, heart rate variability as a measure of autonomic control has been shown to be significantly decreased in patients who are taking donepezil, although this result was not compared with a placebo (McLaren et al, 2003).
| Box 1 A clarification of bradycardia Sinus node disease Usually caused by ischaemia, infarction or degenerative disease and results in long intervals between each atrial depolarisation. A prolonged interval between consecutive P-waves (>2 s) is seen on the ECG. Cardiac pacing is indicated for chronic symptomatic sinus node disease. Atrioventricular (AV) block Affects the conduction of depolarisation between the atria and ventricles:
Mobitz type 1 second-degree AV block is the most benign. Patients with Mobitz type 2 and advanced second-degree AV block are at risk of progressing to complete heart block and are more likely to require cardiac pacing.
Intraventricular conduction disturbance Within the ventricles, a number of conduction disturbances can occur. Blocked conduction at the bundle of His causes AV block. Block of the right or left bundle branches causes a widening of the QRS complexes. Patients may be asymptomatic, or may complain of syncope due to intermittent complete heart block or ventricular tachycardias.
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The critical question is the clinical significance of these physiological changes, since although small changes in heart rate are unlikely to have a clinical impact, profound sinus bradycardia or bradycardia due to second- or third-degree heart block have the potential to precipitate heart failure, syncope or seizures.
| Evidence of cardiovascular adverse events in trials |
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Although all three drugs led to a significantly higher incidence of dose-related dizziness (Corey-Bloom et al, 1998; Rosler et al, 1999; Birks et al, 2000; Evans et al, 2004; Birks & Harvey, 2006; Loy & Schneider, 2006), its cause is multifactorial, and investigators have tended to regard dizziness as a neurological rather than a cardiovascular adverse effect.
A Cochrane review of pooled data from RCTs of all three AChE inhibitors (Birks, 2006) showed the incidence of syncope to be significantly higher in patients given an AChE inhibitor compared with those given a placebo (3.43 v. 1.87%, P = 0.02). Syncope has been noted as a serious adverse effect in active treatment with donepezil (n = 10) (Rogers et al, 1998; Mohs et al, 2001; Winblad et al, 2001; Seltzer et al, 2004). Half of these were considered by authors to be unrelated to donepezil and three resulted in treatment withdrawal.
The Cochrane review also reported that pooled data from unpublished studies on the use of galantamine in people with mild cognitive impairment who were at risk of developing Alzheimers disease found a significantly higher rate of unexplained death in those given the drug (Loy & Schneider, 2006). As a result, it recommended that galantamine should not be used in mild cognitive impairment until there is evidence that supports or disproves the unpublished findings.
None of the RCTs we analysed showed consistent clinically significant differences between the effect of the drug and placebo on pulse, blood pressure or ECG. The higher incidence of sinus bradycardia in those treated with donepezil compared with placebo in four studies was not significant (Tariot et al, 2000; Feldman et al, 2001; Winblad et al, 2001; Black et al, 2003), and an analysis of four RCTs of rivastigmine (Morganroth et al, 2002) showed no differences in heart rate or ECG indices (including PR and QT intervals) between rivastigmine and placebo.
The incidence of ischaemic heart disease found during the trials was low and not significantly greater than in an equivalent comparison population. In addition, a number of studies demonstrated that populations with pre-existing cardiovascular disease or high rates of concurrent medication use showed no greater occurrence of cardiovascular adverse events (Kumar et al, 2000; Tariot et al, 2001; Black et al, 2003).
Birks (2006) analysis of the limited number of head-to-head trials (Bullock et al, 2001; Wilcock et al, 2003; Jones et al, 2004; Bullock et al, 2005) revealed no consistent evidence of a difference in cardiovascular side-effect profile between the three drugs.
Open-label studies
The shortcomings of RCTs are their short duration and selective entry criteria. We must rely on reports from clinical practice and open-label studies to reveal rarer, idiosyncratic and delayed adverse effects. Numerous open-label studies have been carried out, although the weight of evidence they provide is restricted by the absence of control groups. Here we report on ten of these (for a list of the studies and the cardiovascular adverse effects reported see Table DS2 in the online data supplement to this article).
The longest period of continuous use of AChE inhibitors was 4 years. There was no evidence of an association between longer duration of use and increased incidence of cardiovascular adverse events such as bradycardia, syncope and dizziness. Furthermore, the cardiovascular safety profile of the AChE inhibitors was found to be the same in a real-world study with few exclusion criteria (Mossello et al, 2004). We found no reports of direct drug interactions, and one trial with donepezil (Relkin et al, 2003) demonstrated that the risk of clinically important bradycardia is not significantly increased by concurrent use of beta-blockers, calcium antagonists or digoxin.
A statistically insignificant mean drop in heart rate of two beats per minute and rise in the PR interval (3 ms) was seen in patients taking donepezil, but neither observation was related to clinical adverse events (Froelich et al, 2004). The same study showed that patients with pre-existing first-degree heart block were no more likely to progress to second-degree or complete heart block while on treatment, and pre-morbid cardiovascular disease was not associated with a significantly increased incidence of cardiovascular adverse effects.
Case studies
Between 1997 and 1999 in the UK, the Committee on Safety of Medicines and the Medicines Control Agency received four reports of heart block in patients receiving donepezil (one first-degree, two second-degree and one complete heart block), and 20 reports of seizure (Anonymous, 1999).
Seven cases of new-onset bradycardia presenting as syncope, and thought to be related to donepezil, have been reported (Bordier et al, 2006). Three occurred early after drug initiation; the others occurred well into treatment. On investigation, four of the patients were found to have carotid sinus hypersensitivity and three sinus node disease. Two of the patients had seizures following ventricular standstill. The causal relationship between AChE inhibitors and these events remains unclear. Cardiac pacing systems were fitted in all seven patients, and they continued donepezil.
Newby et al(2004) reported second-degree and complete heart block in a previously asymptomatic individual who suffered syncope and seizures 1 week after beginning donepezil. Similar atrioventricular rhythm disturbances associated with syncope were also reported in a French case study 3 h after a patient received galantamine (Brembilla-Perrot et al, 2004).
A Spanish case study reported a case of symptomatic sinus bradycardia on donepezil initiation, causing left ventricular failure (Calvo-Romero & Ramos-Salado, 1999). The pulse rate returned to normal on discontinuation of the drug.
Finally, there has been a case report of QT interval prolongation after beginning rivastigmine, although this may have been complicated by medical comorbidity, electrolyte disturbance or polypharmacy (Walsh & Dourish, 2002).
| Putting the evidence into practice |
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Criteria developed by Wilson & Jungner (1968) have been used widely in assessing whether or not to implement population screening programmes, and the guidelines we outline here for managing cardiovascular risk with AChE inhibitors were developed with these criteria in mind. Wilson & Jungner state that a screening tool should be used for conditions that cause significant morbidity and have a well-understood natural history of a preclinical asymptomatic phase that can be detected accurately and in a resource-efficient manner.
The incidence of cardiovascular adverse events with AChE inhibitors is low. Rarely, they appear to cause or unmask parasympathetically mediated bradycardias, and in a minority of people this may be associated with serious consequences. On the weight of existing evidence, intensive cardiac screening is not justified, as it produces little clinical benefit with potentially major resource implications. Furthermore, although people with sick sinus syndrome or other cardiac conduction defects may be at a theoretically greater risk of developing cardiovascular adverse effects with AChE inhibitors, additional evidence is needed to confirm this relationship in clinical practice. Currently, there is not sufficient evidence to suggest any high-risk groups that could be targeted for screening.
ECGs and cardiac monitoring
The use of ECGs before instigation of therapy is unlikely to be helpful and is not recommended. Trial evidence indicates that abnormal ECGs are not predictive of cardiovascular adverse events, and that such events also occur in those with a normal pre-treatment ECG. In addition, cardiac monitoring for 2448 h could not be justified as a screening tool since it is a relatively insensitive method of detecting arrhythmias, is poorly tolerated and has high resource implications.
Drug interactions
Although clinicians should be aware of the potential for synergy between AChE inhibitors and drugs that reduce heart rate (e.g. digoxin and beta-blockers), evidence does not support the need to routinely stop these medications before starting AChE inhibitor treatment.
| A clinical protocol |
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Box 2 Key points for the clinician
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If a patient taking an AChE inhibitor presents with syncope or seizures an underlying cardiovascular cause should be strongly suspected (Thompson et al, 2004). The drug should be stopped and the patient referred to a physician for further investigation. If examination reveals no causal relationship with the drug, or if a pacemaker is fitted, the drug may be restarted.
Symptoms such as falls and dizziness often have complex and multifactorial causes, with dizziness tending to be transient and usually unrelated to cardiovascular problems. Referral to an elderly care physician for multidisciplinary assessment should be considered in these situations (Box 3
).
Box 3 Dealing with dizziness
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The protocol and guidelines outlined here should be regularly audited to test their efficacy in detecting cardiovascular problems and to assess the quantity and quality of referrals generated. As new evidence comes to light, the guidelines may need to be reviewed and modified as appropriate.
| Declaration of interest |
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MCQ answers
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| Footnotes |
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For a commentary on this article see pp. 185186, this issue. This paper has been corrected post-publication, in deviation from print and in accordance with a printed corrigendum to appear in the July issue of the journal.
1 Interpretation of ECGs is discussed in Abdelmawla, N. & Mitchell, A. (2006) Sudden cardiac death and antipsychotics. Part 2: Monitoring and prevention. Advances in Psychiatric Treatment, 12, 100109. Heart block and general heart function are discussed in OBrien, P. & Oyebode, F. (2003) Psychotropic medication and the heart. Advances in Psychiatric Treatment, 9, 414423 (both articles may be accessed free from http://apt.rcpsych.org). Ed. ![]()
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