Biomedical subjects
Publications and source records attributed to Faizel Osman.
Ventricular tachycardia (VT) can be a life threatening condition which can be caused by an underlying electrolyte disturbance, such as hypomagnesaemia. Causes of electrolyte disturbances, such as magnesium losing nephropathy, should be identified early to allow correct management of the underlying cause of the cardiac arrhythmia.
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A 46-year old lady was under regular follow up for aortic valve replacement done in 2002 for aortic stenosis. The valve was a Carbomedics 19 mm bi-leaflet aortic valve prosthesis for which she had adequate anticoagulation since implantation. She had a past history of end stage renal failure, type 2 diabetes, hypertension, cerebrovascular disease and systemic lupus erythematosus. She was asymptomatic and had a routine transthoracic echocardiogram performed which revealed that her aortic valve prosthesis was well seated with an elevated velocity across the valve; the aortic valve leaflets were poorly visualised but appeared to be mobile. A transoesophageal echocardiogram (TOE) confirmed the markedly increased forward velocity across the aortic valve (maximum velocity 4.6 m/s) with small aortic root raising the possibility of pressure recovery phenomenon. Once again the leaflets were not clearly seen but appeared mobile despite the use of deep trans-gastric view. Fluoroscopy was performed and revealed that one of the leaflets was not moving. The patient had an intra-cardiac ultrasound scan (ACUSON AcuNav; Siemens) with the probe of the scanner within the right atrium. A long-axis view demonstrated the prosthetic aortic valve leaflets clearly (Fig. 1). A short-axis view of the prosthetic valve revealed an echogenic area at the six o'clock position; this may be due to pannus formation (Fig. 2); colour flow across the valve during systole revealed absence of colour flow though one of the leaflets due to the leaflet being stuck (Fig. 3). The sewing cuff of the Carbomedics valve is coated with biolite carbon, which is an anti-thrombotic agent that prevents adhesion of thrombus or pannus on the sewing cuff. There are few reports of Carbomedics valve dysfunction by pannus formation in the mitral position but none in the aortic position. Fluoroscopy can be used to visualize mobility of valve leaflets but is unable to identify thrombus/pannus formation that may be causing the valve to stick. Intra-cardiac echocardiography (ICE) can provide additional information regarding potential causes of valve dysfunction such as pannus/thrombus formation. However, ICE does suffer from the same limitations as TOE in obtaining sufficiently adequate images of the aortic valve to allow appropriate assessment of leaflet motion and insight into flow channels; it is also more invasive and expensive compared with other imaging modalities. In our patient ICE provided better images than TOE, possibly due to the closer proximity of the probe to the aortic root compared with TOE. ICE is a novel tool in the assessment of prosthetic valve function, which can complement data obtained from transthoracic/transoesophageal echocardiography and fluoroscopy.
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The present case report describes a 54-year-old woman with recurrent syncope of undetermined etiology. Despite several cardiological and neurological investigations, no firm diagnosis was established until an insertable loop recorder (REVEAL Plus Model 9526, Medtronic Inc., Minneapolis, MN, USA) revealed muscle twitch artifact secondary to a seizure disorder.
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Patients with subclinical and treated overt hyperthyroidism have an excess vascular mortality rate. Several symptoms and signs in overt hyperthyroidism suggest abnormality of cardiac autonomic function that may account in part for this excess mortality rate, but few studies have examined cardiac autonomic function in untreated and treated hyperthyroidism. We assessed heart rate turbulence (HRT) and time-domain parameters of heart rate variability in a large, unselected cohort of patients with overt hyperthyroidism referred to our thyroid clinic (n = 259) and compared findings with a group of normal subjects with euthyroidism (n = 440). These measures were also evaluated during antithyroid therapy (when serum-free thyroxine and triiodothyronine concentrations returned to normal but thyrotropin remained suppressed (i.e., subclinical hyperthyroidism, n = 110) and when subjects were rendered clinically and biochemically euthyroid (normal serum thyrotropin, free thyroxine and triiodothyronine concentrations, n = 219). We found that overall measures of heart rate variability and those specific for cardiac vagal modulation were attenuated in patients with overt hyperthyroidism compared with normal subjects; measurements of overall heart rate variability remained low in those with low levels of serum thyrotropin but returned to normal in patients with biochemical euthyroidism. Measurements of HRT (onset and slope) were also decreased in patients with overt hyperthyroidism, but HRT slope returned to normal values with antithyroid treatment. This study is the first to evaluate HRT in overt and treated hyperthyroidism.
BACKGROUND: Amiodarone-induced thyrotoxicosis (AIT) is a difficult management problem about which there are little published data. We examined whether continuing amiodarone or differentiating AIT into 2 subtypes affected outcome. METHODS AND RESULTS: The type and duration of antithyroid treatment and response were recorded in a consecutive series of 28 cases. Comparisons were made between those in whom amiodarone either was continued or stopped and between those with either possible type 1 or type 2 AIT. Of the 28 cases, 5 had spontaneous resolution of AIT; 23 received carbimazole (CBZ) alone as first-line therapy. Eleven achieved long-term euthyroidism off CBZ or on a maintenance dose. Five became hypothyroid and required long-term thyroxine. Five relapsed after stopping CBZ treatment and were rendered euthyroid with either long-term CBZ (n=3) or radioiodine (n=2). Four were intolerant of CBZ and received propylthiouracil (PTU), with good effect in 3. One was resistant to thionamide alone (CBZ then PTU) and responded to adjunctive steroids. No difference in presentation or outcome was noted between those in whom amiodarone was continued or stopped or between possible type 1 or type 2 AIT. CONCLUSIONS: Continuing amiodarone has no adverse influence on response to treatment of AIT. First-line therapy with a thionamide alone is appropriate in iodine-replete areas, thus avoiding potential complications of other drugs. Differentiating between 2 possible types of AIT does not influence management or outcome.
Hyperthyroidism is a common disorder affecting multiple systems in the body. The cardiovascular effects are among the most striking. The availability of effective treatments for hyperthyroidism has led to the widespread perception that it is a reversible disorder without any long-term consequences. Recent evidence suggests, however, that there may be adverse outcomes. Long-term follow-up studies have revealed increased mortality from cardiovascular and cerebrovascular disease in those with a past history of overt hyperthyroidism treated with radioiodine, as well as those with subclinical hyperthyroidism. Thyroid hormones are known to exert direct effects on the myocardium, as well as the systemic vasculature and predispose to dysrhythmias, especially supraventricular. Atrial fibrillation (AF) is a recognized complication of overt hyperthyroidism, and subclinical hyperthyroidism is also known to be a risk factor for development of AF. Supraventricular dysrhythmias, particularly atrial fibrillation, in older patients may account for some of the excess cardiovascular and cerebrovascular mortality described, especially because AF is known to predispose to embolic phenomena.
Thyrotoxicosis is often perceived as a reversible disorder without long-term consequences, perhaps because of the availability of effective treatments, but recent evidence suggests that there may, in fact, be adverse outcomes. Long-term follow-up studies have revealed increased mortality from cardiovascular and cerebrovascular disease in those with a past history of overt hyperthyroidism treated with radioiodine as well as in those with subclinical hyperthyroidism indicated by a low serum TSH concentration. Thyroid hormones exert direct effects on the myocardium as well as the systemic vasculature predisposing to dysrhythmias, especially supraventricular. Effects of thyroid hormones on the autonomic nervous system may also contribute to arrhythmogenesis. Atrial fibrillation is a recognized complication of hyperthyroidism that predisposes to embolic events. Development of atrial fibrillation, together with other supraventricular dysrhythmias (both clinically obvious and those detected only by Holter monitoring) in those with hyperthyroidism may account for increased vascular mortality. Improved detection of supraventricular dysrhythmias and therapeutic intervention (e.g. anticoagulants, antiarrhythmics) may improve the long-term vascular prognosis, but their role remains to be established in large therapeutic trials.