Drug-related syncope

Evaluation of Patients with Syncope in the Emergency Department: How to Adjust Pharmacological Therapy

The rate of syncope in the Emergency Department ranges between 0.9 and 1.7%. Syncope is mostly related to a underlying reflex or orthostatic mechanism. A bradycardic or a hypotensive phenotype, may be identified. The latter is the most common and could be constitutional or drug induced. Consequently, obtaining an accurate drug history is an important step of the initial assessment of syncope. As anti-hypertensive medication might be responsible for orthostatic hypotension, managing hypertension in patients with syncope requires finding an ideal balance between hypotensive and cardiovascular risks. The choice of anti-hypertensive molecule as well as the therapeutic regimen and dosage, influences the risk of syncope. Not only could anti-hypertensive drugs have a hypotensive effect but opioids and psychoactive medications may also be involved in the mechanism of syncope. Proper drug management could reduce syncope recurrences and their consequences.

Loss of Consciousness in the Young Child

In the very young child (less than eight years of age), transient loss of consciousness represents a diagnostic and management dilemma for clinicians. While most commonly benign, syncope may be due to cardiac dysfunction which can be life-threatening. It can be secondary to an underlying ion channelopathy, cardiac inflammation, cardiac ischemia, congenital heart disease, cardiomyopathy, or pulmonary hypertension. Patients with genetic disorders require careful evaluation for a cardiac cause of syncope. Among the noncardiac causes, vasovagal syncope is the most common etiology. Breath-holding spells are commonly seen in this age group. Other causes of transient loss of consciousness include seizures, neurovascular pathology, head trauma, psychogenic pseudosyncope, and factitious disorder imposed on another and other forms of child abuse. A detailed social, present, past medical, and family medical history is important when evaluating loss of consciousness in the very young. Concerning characteristics of syncope include lack of prodromal symptoms, no preceding postural changes or occurring in a supine position, after exertion or a loud noise. A family history of sudden unexplained death, ion channelopathy, cardiomyopathy, or congenital deafness merits further evaluation. Due to inherent challenges in diagnosis at this age, often there is a lower threshold for referral to a specialist.

Combined hypertension and orthostatic hypotension in older patients: a treatment dilemma for clinicians

The combination of hypertension and orthostatic hypotension in older individuals is becoming increasingly recognized. Managing this combination of disorders presents a treatment dilemma -- how to lower blood pressure to provide cardiovascular risk protection without predisposing to syncope. At present, there is no specific evidence base available with regard to managing such patients. Some antihypertensive drug classes (e.g., alpha-blockers) appear more problematic in this regard than others. In the absence of controlled-trial evidence, use of antihypertensives with a more gradual onset of effect commenced at lower doses and use of lower-limb compression hosiery appears to be a reasonable approach. Abdominal compression devices and elevating the head of the bed may also help to combat orthostatic hypotenstion in older patients with hypertension and warrant future research.

Use of antiarrhythmic drugs in elderly patients

Human aging is a global issue with important implications for current and future incidence and prevalence of health conditions and disability. Cardiac arrhythmias, including atrial fibrillation, sudden cardiac death, and bradycardia requiring pacemaker placement, all increase exponentially after the age of 60. It is important to distinguish between the normal, physiological consequences of aging on cardiac electrophysiology and the abnormal, pathological alterations. The age-related cardiac changes include ventricular hypertrophy, senile amyloidosis, cardiac valvular degenerative changes and annular calcification, fibrous infiltration of the conduction system, and loss of natural pacemaker cells and these changes could have a profound effect on the development of arrhythmias. The age-related cardiac electrophysiological changes include up- and down-regulation of specific ion channel expression and intracellular Ca(2+) overload which promote the development of cardiac arrhythmias. As ion channels are the substrates of antiarrhythmic drugs, it follows that the pharmacokinetics and pharmacodynamics of these drugs will also change with age. Aging alters the absorption, distribution, metabolism, and elimination of antiarrhythmic drugs, so liver and kidney function must be monitored to avoid potential adverse drug effects, and antiarrhythmic dosing may need to be adjusted for age. Elderly patients are also more susceptible to the side effects of many antiarrhythmics, including bradycardia, orthostatic hypotension, urinary retention, and falls. Moreover, the choice of antiarrhythmic drugs in the elderly patient is frequently complicated by the presence of co-morbid conditions and by polypharmacy, and the astute physician must pay careful attention to potential drug-drug interactions. Finally, it is important to remember that the use of antiarrhythmic drugs in elderly patients must be individualized and tailored to each patient's physiology, disease processes, and medication regimen.

Strategy for the management of vasovagal syncope

The disorders of autonomic control associated with orthostatic intolerance are a diverse group of syndromes that can result in syncope and near-syncope. A basic understanding of the pathophysiology of these disorders is essential to diagnosis and proper treatment. It is especially important to recognise the difference between the effect of prolonged upright posture on a failing autonomic nervous system (a hyposensitive or dysautonomic response) and the vasovagal response (which may be a hypersensitive response). Vasovagal syncope is the most common abnormal response to upright posture and occurs in all age groups. The advent of tilt table testing has helped define a population with an objective finding during provocative testing that has enabled researchers to study the mechanism of vasovagal syncope and to evaluate the efficacy of treatments. In most patients, vasovagal syncope occurs infrequently and only under exceptional circumstances and treatment is not needed. Treatment may be indicated in patients with recurrent syncope or with syncope that has been associated with physical injury or potential occupational hazard. Based on study data, patients with vasovagal syncope can now be risk stratified into a high-risk group likely to have recurrent syncope and a low-risk group. Many patients with vasovagal syncope can be effectively treated with education, reassurance and a simple increase in dietary salt and fluid intake. In others, treatment involves removal or avoidance of agents that predispose to hypotension or dehydration. However, when these measures fail to prevent the recurrence of symptoms, pharmacological therapy is usually recommended. Although many pharmacological agents have been proposed and/or demonstrated to be effective based on nonrandomised clinical trials, there is a remarkable absence of data from large prospective clinical trials. Data from randomised placebo-controlled studies support the efficacy of beta-blockers, midodrine, serotonin reuptake inhibitors and ACE inhibitors. There is also considerable clinical experience and a consensus suggesting that fludrocortisone is effective. Encouraging new data suggest that a programme involving tilt training can effectively prevent vasovagal syncope. For patients with recurrent vasovagal syncope that is refractory to these treatments, implantation of a permanent pacemaker with specialised sensing/pacing algorithms appears to be effective. A number of larger clinical trials are underway which should help further define the efficacy of a number of different treatments for vasovagal syncope.

Potential drug-drug interactions in elderly patients presenting with syncope

Adverse drug reactions and interactions are a common cause of iatrogenic disease. Although there are resources available that have been developed for assessing potential drug-drug interactions (DDIs), one must first consider the possibility in order to apply these tools. This cross-sectional analysis of elderly patients evaluates Emergency Physician documentation of potential DDIs and assesses the utility of computer software recognition of interactions that can lead to syncope. In this study, lack of documentation of a patient's past medical history and medications suggests that Emergency Physicians are not evaluating DDIs as a possible source of their patient's symptoms. The computer resources evaluated were found to be easy to use and reliable. Rectifying and preventing potential DDIs can be an indispensible service provided by the Emergency Physician.

Withdrawing cardiovascular medications at a syncope clinic

It is widely assumed in clinical practice that drug treatment associated with hypotension can result in falls and syncope, but there is actually very little evidence to support this. Therefore the data in all patients whose cardiovascular medications were stopped at a falls/syncope clinic were analysed to see if their symptoms were altered and if renewal of these medications was necessary at subsequent visits. Of 338 consecutive referrals, cardiovascular medications had been stopped in 65 (19%). At follow up 78% reported improvement in their original presenting symptoms and renewal of medication was not necessary in 77% off antianginals, 69% off antihypertensives, and 36% off antiarrhythmics. It was concluded that adjusting cardiovascular medications could help in the management of falls and syncope and may obviate the need for other treatment. These medications can be stopped in select patients if there is regular monitoring and this should reduce unwanted side effects and costs of these drugs.

Putting it together: a new treatment algorithm for vasovagal syncope and related disorders

The consensus process that culminated in this symposium established an algorithm to guide the diagnosis and treatment of patients with vasovagal syncope and related disorders. In some patients, the hemodynamic response to standing may identify an abnormality-postural orthostatic tachycardia syndrome or orthostatic hypotension-that can often be treated without further testing. When the response to standing is normal, tilt-table testing may be useful in making the diagnosis of vasovagal syncope and guiding treatment. In some patients, however, the diagnosis is clear from the history, and tilt-table testing may not be necessary. Not all patients with vasovagal syncope need to be treated, and many can be treated effectively with education, reassurance, and a simple increase in dietary salt. In evaluating the results of tilt-table testing, an important consideration is the distinction between vasovagal syncope and the dysautonomic response to tilt characterized by a gradual and progressive decrease in blood pressure that leads to syncope. Current practice patterns suggest that beta blockers, fludrocortisone, and midodrine, are commonly used to treat patients with vasovagal syncope, and patients with the dysautonomic response are generally treated with fludrocortisone and midodrine. Permanent pacing with specialized pacing algorithms should be considered for patients with frequent vasovagal syncope that is refractory to medical therapy. The guidelines proposed here are an amalgam of clinical experience, expert opinion, and research evidence; however, they do not suggest a standard of care for all patients.

Effects of long-term vasodilator therapy in patients with carotid sinus hypersensitivity

BACKGROUND

In patients affected by carotid sinus hypersensitivity, long-term vasodilator therapy might increase the risk of syncopal episodes by reducing systolic blood pressure and venous return to the heart.

METHODS AND RESULTS

Thirty-two patients (mean age 73 +/- 9 years; 20 men) who met all the following criteria were included: (1) one or more episodes of syncope occurring during long-term (>6 months) treatment with angiotensin-converting enzyme inhibitors, long-acting nitrates, calcium antagonists, or a combination of these; (2) a positive response to carotid sinus massage, defined as the reproduction of spontaneous syncope in the presence of ventricular asystole > or =3 seconds or a fall in systolic blood pressure > or =50 mm Hg; (3) negative workup for other causes of syncope. The patients were randomly assigned to continue or to discontinue use of vasodilators; carotid sinus massage was repeated 2 weeks after randomization. By the end of the study period, the baseline values of systolic blood pressure were significantly different between the 2 groups of patients both in supine (P=.01) and upright (P=.03) positions. Syncope had been induced by carotid sinus massage in 81% of patients in the "on-vasodilator" group and in 62% of patients in the "off-vasodilator" group (P=.21). The cardioinhibitory reflex was of similar magnitude in the 2 groups, being found in 50% of the patients in each group, with a maximum ventricular pause of 7.1 +/- 2.7 and 6.7 +/- 1.8 seconds, respectively. The percentage decrease of blood pressure did not differ between the 2 groups, even if, in absolute values, the baseline difference of blood pressure roughly persisted for the duration of the test. In consequence of that, the rise of blood pressure to similar values was delayed approximately 30 seconds in the "on-vasodilator" group and took more than 2 minutes to return to baseline values.

CONCLUSIONS

In patients affected by carotid sinus hypersensitivity, chronic vasodilator therapy does not have a direct effect on carotid sinus reflexivity, although the delayed recovery of pretest blood pressure values could indirectly potentiate the severity of the clinical manifestations of the syndrome. The persistence of hypotension for a longer time after the end of the massage suggests that vasodilators cause an impairment of compensatory mechanisms.

Effects of chronic vasodilator therapy to enhance susceptibility to vasovagal syncope during upright tilt testing

To evaluate the effect of chronic vasodilator therapy on susceptibility to vasovagal syncope, 45 patients with syncope and a positive response to tilt testing were randomly assigned to continue or to discontinue vasodilators. The study result demonstrated that chronic vasodilator therapy enhances susceptibility to vasovagal reaction during upright tilt testing.

Orthostatic hypotension in older adults. The Cardiovascular Health Study. CHS Collaborative Research Group

The purpose of the present study was to assess the prevalence of orthostatic hypotension and its associations with demographic characteristics, cardiovascular risk factors and symptomatology, prevalent cardiovascular disease, and selected clinical measurements in the Cardiovascular Health Study, a multicenter, observational, longitudinal study enrolling 5,201 men and women aged 65 years and older at initial examination. Blood pressure measurements were obtained with the subjects in a supine position and after they had been standing for 3 minutes. The prevalence of asymptomatic orthostatic hypotension, defined as 20 mm Hg or greater decrease in systolic or 10 mm Hg or greater decrease in diastolic blood pressure, was 16.2%. This prevalence increased to 18.2% when the definition also included those in whom the procedure was aborted due to dizziness upon standing. The prevalence was higher at successive ages. Orthostatic hypotension was associated significantly with difficulty walking (odds ratio, 1.23; 95% confidence interval, 1.02, 1.46), frequent falls (odds ratio, 1.52; confidence interval, 1.04, 2.22), and histories of myocardial infarction (odds ratio, 1.24; confidence interval, 1.02, 1.50) and transient ischemic attacks (odds ratio, 1.68; confidence interval, 1.12, 2.51). History of stroke, angina pectoris, and diabetes mellitus were not associated significantly with orthostatic hypotension. In addition, orthostatic hypotension was associated with isolated systolic hypertension (odds ratio, 1.35; confidence interval, 1.09, 1.68), major electrocardiographic abnormalities (odds ratio, 1.21; confidence interval, 1.03, 1.42), and the presence of carotid artery stenosis based on ultrasonography (odds ratio, 1.67; confidence interval, 1.23, 2.26). Orthostatic hypotension was negatively associated with weight. We conclude that orthostatic hypotension is common in the elderly and increases with advancing age. It is associated with cardiovascular disease, particularly those manifestations measured objectively, such as carotid stenosis. It is associated also with general neurological symptoms, but this link may not be causal. Differences in prevalence of and associations with orthostatic hypotension in the present study compared with others are largely attributed to differences in population characteristics and methodology.

Syncope

Syncope is a clinical entity of diverse cause. The historical features surrounding the syncopal event and the presence or absence of heart disease are the most important features in establishing the cause for syncope. Passive head-up tilt study provides a means of identifying many patients with vasodepressor syncope. Electrophysiologic study is important in the elucidation of syncope in patients who have syncope undefined after noninvasive evaluation. With proper use of the modalities available, few patients will have an undefined cause for syncope.

The etiology of syncope in pacemaker patients

A total of 46 patients with syncopal episodes after VVI pacemaker implantation were studied. Of these, 92% had one to three syncopal episodes and 8% more than three. All underwent a thorough clinical examination, which included chest X ray, echocardiogram, neurological exam, and the following protocol: 24-hour Holter monitoring, EEG, blood pressure (BP) measurement in three positions, Doppler exam of the carotid vessels, fasting blood glucose, and head-up tilt table test (60 minutes, 60 degrees). Holter monitoring showed exit block in two patients (4.3%) and failed sensing in one (2.1%). In two patients there was unilateral slowing on EEG. Orthostatic hypotension was found in four patients (8.6%), and hypoglycemia in three insulin-dependent diabetics. An occlusive atherosclerotic plaque in the carotid artery was found in three patients (6.5%). Syncope was induced in 17 patients (36.9%) by the tilt table test, after a mean standing time of 47 +/- 11 minutes. The mean resting systolic BP of these patients was 140 +/- 24 mmHg, and fell to a mean level of 56 +/- 8 mmHg (mean systolic BP drop was 79 +/- 8 mmHg). Sixteen of these 17 patients with positive tilt table were being paced at the time of syncope and one had a spontaneous heart rate of 73 beats/min. In 14 cases (30.4%) the cause of syncopal episodes after this extensive workup remained unexplained. These results indicate that pacemaker dysfunction is not a major cause of syncopal episodes in pacemaker patients and that these are most often due to vasovagal syncope. Long-term follow-up is warranted to determine the prognostic significance of various types of syncope in pacemaker patients.