Abstract
Case history
A 99-year-old man was admitted to hospital as an emergency from home due to progressively declining cognition, poor memory, features of depression and reduced mobility over an 8 week period. His son described him as previously independent and self-caring.
Approximately 8 weeks before admission, his son had taken the patient to see his GP. He had not had contact with health services in the preceding 20 years. The GP did not know the patient as he had never attended the surgery but agreed the patient appeared vague, withdrawn and mentally slow. He referred him to the local day hospital for further assessment (4 weeks prior to the acute admission). At this time, he scored 6/10 on Abbreviated Mental Test (AMT), 22/30 on Mini-Mental State Examination (MMSE) and 9/15 on Geriatric Depression Scale (GDS). Neurological examination was normal. Pulse was recorded as 55 beats per minute (bpm) and blood pressure 150/86 mmHg. Blood tests excluded anaemia, thyroid dysfunction, renal or liver impairment. Serum calcium was normal. Urinalysis was unremarkable. A diagnosis of depression with associated mood-congruent cognitive impairment was made, citalopram was prescribed and follow-up planned.
At the time of acute admission, the patient's mental state assessment was unchanged. He could not walk unaided or feed himself. His son noted that he had become unkempt and virtually uncommunicative in the preceding 2 weeks. His radial pulse was 27 bpm and electrocardiogram (ECG) confirmed the presence of complete heart block with no features of an acute myocardial infarction (Fig. 1). Transthoracic echocardiography was normal. Blood pressure was maintained at 138/88 mmHg. There were no features of an acute neurological event and computed tomography of the head showed age-related cerebral atrophy without evidence of other pathology.
A diagnosis of chronic complete heart block was made. Citalopram was discontinued. A single chamber VVI permanent pacemaker (which paces the ventricle but is inhibited by a sensed native heart beat) was subsequently inserted. Two weeks later, the patient was self-caring and walking with a stick. Repeat assessment of mental function revealed scores of 10/10 on AMT, 28/30 on MMSE and 1/15 on GDS. The native heart rhythm remained complete heart block despite withdrawal of citalopram.
Complete heart block (Third-degree atrioventricular block).
Potential causes of delirium
Discussion
Assessment of elderly patients with cognitive decline is frequently required in general practice. One key feature in determining the underlying cause is the time scale of onset. The fairly rapid onset in this patient suggests that he was suffering from an acute form of cognitive decline (i.e. delirium) rather than the gradual progressive decline of chronic cognitive impairment, such as is seen in vascular or Alzheimer's dementia. His symptoms were consistent with hypoactive delirium. Most people think that agitated hyperactive delirium is the most common picture but the hypoactive subtype is actually more frequent and has a poorer prognosis.
Delirium in the elderly is common and frequently results in hospital referral. Some aetiologies cause rapid deterioration in cognition, while others are less obvious, resulting in a less dramatic slower onset delirium (Table 1). Patients require careful evaluation to exclude these possibilities.
While depression and features of a depressive illness are common in the elderly and frequently associated with failing cognition, a rapid decline in cognitive function without other major indicators of depressive illness (such as a significant score on depression rating scale, disturbed sleep and appetite or suicidal ideation) should prompt the search for an alternative or coexistent pathology.
For this patient, the prescription of citalopram may have been important as bradycardia and prolonged corrected QT (QTc) interval have been reported with use of selective serotonin reuptake inhibitors. However, persistence of complete heart block after its cessation suggests that age-related heart block was the underlying diagnosis, which may have initially been intermittent but subsequently persisted.
Complete heart block in the elderly is not uncommon and may provoke a functional decline in motor and neuropsychiatric function. The clear benefit from insertion of a permanent pacemaker in both motor and neuropsychiatric function in our patient not only confirms the benefit of pacemaker insertion in this age group but also underscores the value of looking for alternative explanations for abrupt changes in physical and mental performance.
In cases of acute cognitive decline, the value of obtaining a clear history of the time scale and nature of the decline from the patient or an attendant, allied to an adequate physical examination cannot be overstressed. While scoring systems for underlying age-related illness can be helpful, they should not replace measures such as recording the radial pulse rate manually and performing an ECG if concerns arise as this is a low effort low cost intervention which can lead to dramatic results.