Bactericidal and anti-biofilm effects of uncharged and cationic ultrasound-responsive nitric oxide microbubbles on Pseudomonas aeruginosa biofilms

Bacterial biofilms are a major and ongoing concern for public health, featuring both inherited genetic resistance traits and a conferred innate tolerance to traditional antibiotic therapies. Consequently, there is a growing need for novel methods of drug delivery, to increase the efficacy of antimicrobial agents. This research evaluated the anti-biofilm and bactericidal effects of ultrasound responsive gas-microbubbles (MBs) of either air or nitric oxide, using an in vitro Pseudomonas aeruginosa biofilm model grown in artificial wound medium. The four lipid-based MB formulations evaluated were room-air MBs (RAMBs) and nitric oxide MBs (NOMBs) with no electrical charge, as well as cationic (+) RAMBs⁺ and NOMBs⁺. Two principal treatment conditions were used: i) ultrasound stimulated MBs only, and ii) ultrasound stimulated MBs with a sub-inhibitory concentration (4 µg/mL) of the antibiotic gentamicin. The total treatment time was divided into a 60 second passive MB interaction period prior to 40 second ultrasound exposure; each MB formulation was tested in triplicate. Ultrasound stimulated RAMBs and NOMBs without antibiotic achieved reductions in biofilm biomass of 93.3% and 94.0%, respectively. Their bactericidal efficacy however was limited, with a reduction in culturable cells of 26.9% and 65.3%, respectively. NOMBs with sub-inhibitory antibiotic produced the most significant reduction in biofilm biomass, corresponding to a 99.9% (SD ± 5.21%); and a 99.9% (SD ± 0.07%) (3-log) reduction in culturable bacterial cells. Cationic MBs were initially manufactured to promote binding of MBs to negatively charged biofilms, but these formulations also demonstrated intrinsic bactericidal properties. In the absence of antibiotic, the bactericidal efficacy of RAMB⁺ and NOMB⁺ was greater that of uncharged counterparts, reducing culturable cells by 84.7% and 86.1% respectively; increasing to 99.8% when combined with antibiotic. This study thus demonstrates the anti-biofilm and bactericidal utility of ultrasound stimulated MBs, and specifically is the first to demonstrate the efficacy of a NOMB for the dispersal and potentiation of antibiotics against bacterial biofilms in vitro. Importantly the biofilm system and complex growth-medium were selected to recapitulate key morphological features of in vivo biofilms. The results us offer new insight for the development of new clinical treatments, for example, in chronic wounds.

Dietary Diversity on the Swahili Coast: The Fauna from Two Zanzibar Trading Locales

Occupants of coastal and island eastern Africa-now known as the 'Swahili coast'-were involved in long-distance trade with the Indian Ocean world during the later first millennium CE. Such exchanges may be traced via the appearance of non-native animals in the archaeofaunal record; additionally, this record reveals daily culinary practises of the members of trading communities and can thus shed light on subsistence technologies and social organisation. Yet despite the potential contributions of faunal data to Swahili coast archaeology, few detailed zooarchaeological studies have been conducted. Here, we present an analysis of faunal remains from new excavations at two coastal Zanzibar trading locales: the small settlement of Fukuchani in the north-west and the larger town of Unguja Ukuu in the south-west. The occurrences of non-native fauna at these sites-Asian black rat (Rattus rattus) and domestic chicken (Gallus gallus), as well as domestic cat (Felis catus)-are among the earliest in eastern Africa. The sites contrast with one another in their emphases on wild and domestic fauna: Fukuchani's inhabitants were economically and socially engaged with the wild terrestrial realm, evidenced not only through diet but also through the burial of a cache of wild bovid metatarsals. In contrast, the town of Unguja Ukuu had a domestic economy reliant on caprine herding, alongside more limited chicken keeping, although hunting or trapping of wild fauna also played an important role. Occupants of both sites were focused on a diversity of near-shore marine resources, with little or no evidence for the kind of venturing into deeper waters that would have required investment in new technologies. Comparisons with contemporaneous sites suggest that some of the patterns at Fukuchani and Unguja Ukuu are not replicated elsewhere. This diversity in early Swahili coast foodways is essential to discussions of the agents engaged in long-distance maritime trade.

Rapid diagnosis of massive pulmonary embolism in a district general hospital

Effective treatment of massive pulmonary embolism is more likely if diagnostic tests are rapidly available, including during out-of-hours. An agreed protocol was implemented in November 1997, which allowed initiation of thrombolysis by junior doctors within an hour of clinical suspicion of the diagnosis of massive pulmonary embolism in six patients in the subsequent year. A similar approach could be considered by other acute hospitals.

The effect of orientation on the clarity of Hermann grid illusory lines

To test the hypothesis that Hermann grid illusory lines are most clear when the grid is presented at a 45 deg, each of 20 participants underwent 10 trials in each of two conditions ('make the lines least clear' and 'make the lines most clear') which were run using a method of adjustment. A matched-pairs t-test applied to the means of the two conditions was significant beyond the 0.01 level. One-group t-tests supported the claim that the illusory lines are least clear for a vertical/horizontal orientation of the grid and most clear when it is rotated 45 deg. The results substantiate, in a systematic manner, 70 years of claims about the effects of grid orientation on illusory line clarity.

Health needs assessment in primary care: the evolution of a practical public health approach

The purpose of the paper is to place health needs assessment in its primary care context. This is a dynamic context where changes in policies, staff roles and patient expectations have all to be considered. Given this complexity and the variations between practices, it is necessary to help primary health care teams (PHCTs) to understand their stage of development and how this will directly affect any health needs assessment. The technical and methodological aspects of health needs assessment have been explored and described by others, and that work will not be duplicated here. This paper reviews the health needs assessment (HNA) work of the Ribblesdale Total Purchasing Project (RTPP) and then sets this review against the political, organisational, professional and practical pressures that currently confront primary care. Out of this analysis emerges a diagnostic and development tool which links together, and emphasises the intimate relationships between, five stages of development needed for effective primary care-oriented health needs assessment work. The emphasis is on understanding the place of health needs assessment within the general processes and systems of the primary health care team. The paper concludes by suggesting ways in which public health practitioners and specialists might approach the task of supporting and influencing the evolution of the recently proposed Primary Care Groups and Primary Care Trusts. The overall intention of the article is to stimulate debate and action.

Detection of viable and non-viable cells in connective tissue explants using the fixable fluoroprobes 5-chloromethylfluorescein diacetate and ethidium homodimer-1

The efficacy of connective tissue explants is difficult to determine, particularly where autopsy material is required for research or clinical applications. We report here an optimised protocol using 5-chloromethylfluorescein diacetate (CMFDA) and ethidium homodimer-1 to distinguish viable and non-viable cells in a range of connective tissue explants. Biopsies and explants of corneae, arteries, cartilage and skin were loaded with fluoroprobes for extended periods (< or = 24h) at low temperatures (4 degrees C), fixed in paraformaldehyde, and processed using a variety of embedding, sectioning, autoradiographic, and immunohistochemical procedures. Detection of fluorescent green CMFDA and red ethidium homodimer was achieved using epi-illuminated light or dual channel confocal microscopy, and clearly differentiated live from dead cells throughout the explants. Furthermore, the intracellular distribution of CMFDA provided superior images of cell shape and morphology not previously available using conventional histochemical techniques. Adaptations of this protocol could prove valuable in a variety of research and clinical applications.

Effects of a patent foramen ovale on arterial saturation during exercise and on cardiovascular responses to deep breathing, Valsalva manoeuvre, and passive tilt: relation to history of decompression illness in divers

OBJECTIVE

To determine whether the presence of a patent foramen ovale could result in significant arterial desaturation and affect the responses of heart rate and blood pressure to physiological manoeuvres and to determine whether responses differed between those with and those without prior clinical events associated with a patent foramen ovale.

DESIGN

Blind controlled study.

SETTING

Teaching hospital.

PATIENTS

Divers with a large patent foramen ovale shown by contrast echocardiography and divided into those who had neurological decompression illness that started within 30 minutes of surfacing (group 1), those who had no history of decompression illness (group 2), and age and sex matched control divers who had no evidence of intracardiac shunts (group 3).

MAIN OUTCOME MEASURES

The change in percentage haemoglobin oxygen saturation during treadmill exercise and the response of heart rate and blood pressure to physiological manoeuvres.

RESULTS

There were no significant differences between the three groups but two divers in group 1 showed clinically important desaturation during exercise and unusual blood pressure and heart rate responses to passive tilt. These divers were notable for having the greatest number of episodes and the most severe single episode of spinal cord decompression illness.

CONCLUSION

A large patent foramen ovale may be associated with clinically significant arterial desaturation and unusual responses of heart rate and blood pressure in some healthy subjects.

Differences in autonomic nerve function in patients with silent and symptomatic myocardial ischaemia

BACKGROUND

Autonomic neuropathy provides a mechanism for the absence of symptoms in silent myocardial ischaemia, but characterisation of the type of neuropathy is lacking.

AIM

To characterise and compare autonomic nerve function in patients with silent and symptomatic myocardial ischaemia.

METHODS AND RESULTS

The Valsalva manoeuvre, heart rate variation (HRV) in response to deep breathing and standing, lower body negative pressure, isometric handgrip, and the cold pressor test were performed by patients with silent (n = 25) and symptomatic (n = 25) ambulatory ischaemia and by controls (n = 21). No difference in parasympathetic efferent function between patients with silent and symptomatic ischaemia was recorded, but both had significantly less HRV in response to standing than the controls (p < 0.005 for silent and p < 0.01 for symptomatic). Patients with silent ischaemia showed an increased propensity for peripheral vasodilatation compared with symptomatic patients (p < 0.02) and controls (p < 0.04). Impaired sympathetic function was found in patients with pure silent ischaemia (n = 4) compared with the remaining patients with silent ischaemia whose pain pathways were presumed to be intact.

CONCLUSIONS

Patients with silent ischaemia and pain pathways presumed to be intact have an enhanced peripheral vasodilator response, and if this applied to the coronary vasculature it could provide a mechanism for limiting ischaemia to below the pain threshold. Patients with pure silent ischaemia have evidence of sympathetic autonomic dysfunction.

Impedance cardiography during exercise in patients with coronary heart disease

Impedance cardiography may be a simple way of assessing left ventricular performance during exercise. Measurements were therefore made during exercise testing in 102 consecutive male patients with suspected coronary disease prior to cardiac catheterization. These were subsequently divided into four groups: group A, normal; group B, 1- or 2-vessel disease; group C, 3-vessel disease (groups A, B, and C, left ventricular ejection fraction (LVEF) > 55%); and group D, 3-vessel disease with LVEF < 55%. Immediately after peak exercise several impedance measures were significantly correlated with resting LVEF, especially dZ/dtmax (R = 0.41, P < 0.001) and Heather index (R = 0.46, P < 0.001). Heather index was the best discriminator between the disease groups with mean values (95% confidence intervals) of 25.7 (22.2-29.2) (group A), 21.9 (20.6-23.2) (group B), 18.4 (16.2-20.6) (group C), and 15.3 (10.3-20.3) omega s-2 (group D) but there was considerable overlap between groups (risk ratios 1.17 and 3.15 for any and triple-vessel coronary disease respectively). Measurements were therefore of little diagnostic value. The majority of patients with abnormal responses could be identified more simply by their poor exercise tolerance or abnormal blood pressure response.

Creatine phosphate (Neoton) as an additive to St. Thomas' Hospital cardioplegic solution (Plegisol). Results of a clinical study

Experimentally, creatine phosphate (CP) added to St. Thomas' Hospital cardioplegic solution (STH) improved post-ischaemic recovery of cardiac function in the rat heart. We investigated the effect of adding CP (10.0 mmol/l) to STH. Fifty open-heart surgery patients were randomized into control (STH) and treated (STH + CP) groups (25 per group). Patients underwent (a) monitoring for peri- and postoperative arrhythmias (48-h Holter monitoring). (b) quantitative birefringence assessment of intraoperative myocardial protection in left and right ventricular biopsies sampled at start of bypass (pre-isch.), end of bypass (end-isch.) and after 10 min reperfusion (post-isch.), and (c) measurement of serum creatine kinase-MB isozyme (CK-MB) values for up to 4 days postoperatively; results were assessed with respect to (d) haemodynamics and postoperative clinical outcome. Inotropic support (adrenaline) was required in three patients (12%) from each group; no patient died. All patients required defibrillation, and the number of direct current shocks required for sinus rhythm was the same in each group. The occurrence and incidence of reperfusion-induced arrhythmias were the same in both groups. Serum CK and CK-MB values were similar throughout the sampling period in both groups of patients; one patient in the control group had raised CK-MB levels postoperatively, but perioperative infarction was not indicated by the electrocardiogram.(ABSTRACT TRUNCATED AT 250 WORDS)

Choosing the pacemaker; a rational approach to the use of modern pacemaker technology

Sophisticated pacemakers now afford greater benefit than only relief of syncope for patients with symptomatic bradyarrhythmia. For clinical reasons it is inappropriate to implant ventricular demand (VVI) pacemakers in every patient, but for both clinical and economic reasons it is also undesirable to use dual-lead or rate-responsive systems indiscriminately. However, the published guidelines for pacemaker choice and investigation are inadequate. We have analysed the clinical assessment and the investigations required in a series of 150 patients with various electrophysiological disorders, considered consecutively for pacemaker implantation using an algorithm to assist decisions. Holter electrocardiography in 77.3%, exercise testing--formal (in 9.3%) or informal (during Holter electrocardiography), electrophysiology study (EPS)--full in 15.3% and partial in 29.3%, and trial of pacing (10.7%) were all used to characterize dysfunction and to define appropriate pacing mode. 142 patients were paced--57.0% with single lead modes (12.7%) AAI, 44.3% VVI) and 43.0% dual-lead (2.8% DVI, 23.9% VDD or VAT, 16.2% DDD). Three patients received rate-responsive systems (VVIR) which, if available, would have been used in nine; four would have been suitable for AAIR and four for dual-lead responsive pacing (DVIR, DDIR or DDDR). We offer a rational approach based on published data for investigation and pacemaker choice in the management of patients with bradyarrhythmia.

Cold-induced pulmonary oedema in scuba divers and swimmers and subsequent development of hypertension

The effect of cold and/or a raised partial pressure of oxygen was examined in eleven people with no demonstrable cardiac abnormality but who had pulmonary oedema when scuba diving or surface swimming, and in ten normal divers. These stimuli induced pathological vasoconstriction in the pulmonary oedema group, nine of whom also showed signs of cardiac decompensation when so stimulated. The pulmonary oedema patients have been followed-up for an average of 8 years. Seven have become hypertensive. Except for the onset of lone atrial fibrillation in one normotensive female diver and development of Raynaud's phenomenon in a normotensive man, there have been no cardiovascular events and no deaths.

Magnesium and coronary revascularization

Twenty patients, who underwent coronary revascularization without cardioplegic arrest, were given (during cardiopulmonary bypass) either magnesium chloride 16 mmol in 10 ml of water (magnesium group) or 10 ml of water alone (control group). Plasma and urinary magnesium concentrations were measured for 24 h after operation. ECG was recorded continuously during this period. QT intervals corrected for heart rate (QTcorr) were calculated from periodic full lead ECG. The mean plasma magnesium concentrations in the control group were less than normal throughout the study, while hypomagnesaemia did not occur in the magnesium group. Urinary magnesium excretion was higher in the magnesium group, with 58% of the administered magnesium excreted in the first 24 h. The observed incidence of frequent or ventricular arrhythmias was 22% in the magnesium group compared with 63% in the control group. No significant differences in QTcorr intervals were observed between the groups.

Assessment of coronary angioplasty: comparison of visual assessment, hand-held caliper measurement and automated digital quantitation

Digital subtraction coronary angiograms (DSA) of 27 patients who had undergone coronary angioplasty (PTCA) to a total of 32 lesions were analyzed using an automated border-detecting computer program and hand-held caliper measurement of diameter percent stenosis. The results were compared with visual interpretation of the 35-mm cineangiograms. Visual reports significantly overestimated the pre-PTCA diameter percent stenosis (P less than .001) and underestimated the residual post-PTCA narrowing compared with the automatic computer program (P less than .001). Caliper measurements overestimated significantly the pre-PTCA stenosis in comparison with the computer (P less than .01), but post-PTCA the two methods did not differ significantly (P = .105). There was a positive but poor correlation between caliper and computer measurements (r = .43, P less than .05) performed on the pre-PTCA digital angiograms. Post-PTCA the two methods correlated better (r = 0.78, P less than .001), but further statistical analysis showed important discrepancies between them. The correlation of visual reports and computer measurements was poor pre-PTCA (Kendall's tau = 0.32, P less than .05) and not statistically significant post-PTCA (tau = 0.64, P = .5). We conclude that there is observer bias in the visual reporting of angioplasty results, so that pre-PTCA lesions are overestimated, whereas post-PTCA are underestimated. Hand-held caliper measurement improves the assessment of coronary stenoses in comparison with the visual report but still may not altogether eliminate observer bias; it may overestimate the pre-PTCA stenoses compared with automated border detection.

Electrocardiography and echocardiography in patients with chest pain and mitral leaflet prolapse

34 patients with catheter verified, haemodynamically trivial mitral leaflet prolapse with chest pain and normal coronary arteries were studied. Nineteen had no auscultatory signs of MLP despite clear catheter or echocardiographic evidence of prolapse. Infero-lateral repolarisation changes on the resting electrocardiogram were present in 29%. 50% had false positive exercise tests. M-mode echocardiography proved diagnostically disappointing but sector scans revealed mitral leaflet prolapse in 62%. The apical 4 chamber acoustic window was markedly superior to the parasternal long axis acoustic window.

Cardiac arrhythmias during anaesthesia for laparoscopy

Fifty-six patients undergoing elective laparoscopy were allocated randomly to two groups. Group H received alcuronium and were ventilated artificially using 0.5% halothane and nitrous oxide in oxygen. Group E breathed spontaneously a mixture of enflurane and nitrous oxide in oxygen. Arterial pressure, heart rate, tidal volume, respiratory rate and end-tidal carbon dioxide tension (PECO2) were monitored. The electrocardiogram (ECG) was recorded continuously using magnetic tape, from before induction until the patient left the recovery area. The incidence of arrhythmias was similar in the two groups. No arrhythmias occurred after the insufflated carbon dioxide had been removed from the abdomen. Spontaneous ventilation with enflurane anaesthesia is a simple and safe, technique for routine laparoscopy, providing the intra-abdominal pressure does not exceed 25 mm Hg.

Cellular sodium concentration and vasoconstrictor state in hypertension

The sodium content of peripheral blood leucocytes was estimated in two separate investigations of the relationship between cellular sodium content and the vasoconstrictor state. In the first study various parameters of forearm blood flow were measured in a group of 31 normal subjects. A positive correlation was found between peripheral vascular resistance and leucocyte sodium content (p less than 0.05), and a negative correlation between venous compliance (VV60) and leucocyte sodium content (p less than 0.001). In the second study the leucocyte sodium content of 14 patients with essential hypertension was investigated before and after treatment with the calcium antagonist verapamil. The sodium content was found to be abnormally high, as previously described, and treatment with verapamil was found to reverse the defect. Both studies indicate a link between cell sodium content and the vasoconstrictor state, and the results are discussed in light of current theory.

The effects of oral digoxin therapy in primary mitral leaflet prolapse

The effects of oral digoxin on symptoms, arrhythmias, exercise tolerance and echocardiographic function in primary mitral leaflet prolapse were studied in 23 patients using a double-blind crossover protocol. Digoxin reduced the incidence and severity of chest pain compared with both the control (P = 0.0002) and placebo (P = 0.0005) periods. We found a high (83%) incidence of predominantly minor arrhythmias on continuous ambulatory monitoring. Digoxin favourably affected the incidence of frequent supraventricular ectopic beats and supraventricular tachycardia but was associated with a significant number (P less than 0.0025) of asymptomatic bradyarrhythmias. In patients with frequent ventricular ectopics, digoxin had no consistent effect. No difference in exercise tolerance between treatment periods was found on maximal treadmill stress testing, but digoxin administration resulted in an increase in echocardiographic mean circumferential fibre shortening velocity (P less than 0.01) and fractional shortening percent (P less than 0.01). This study demonstrates the efficacy of oral digoxin therapy in ameliorating chest pain in patients with primary mitral leaflet prolapse and suggests a favourable effect on supraventricular arrhythmias in such patients.

Cardiac arrhythmias during outpatient dental anaesthesia: comparison of halothane with enflurane

In 75 young female patients undergoing extraction of 3rd molar teeth during halothane or enflurane anaesthesia, the electrocardiogram was recorded on magnetic tape and analysed subsequently for arrhythmias, using a high-speed analyser. Enflurane induced a much lower frequency of arrhythmia during surgery than halothane, but there was otherwise little difference between the two drugs in the quality of anaesthesia or recovery. Many arrhythmias occurred before exposure of the patient to enflurane or halothane; the significance of this is discussed.

The effect of hyperacetatemia on cardiac output during regular hemodialysis

We used impedance cardiography to monitor changes in cardiac output in 22 adult patients with terminal renal failure during hemodialysis against a dialyzate containing acetate. In 7 patients arterial acetate levels rose progressively during dialysis while in the remainder they remained low and steady. Patients who developed hyperacetatemia were able to maintain an elevated cardiac output during dialysis in contrast to the patients with stable acetate levels in whom cardiac output fell. These results strengthen our previous conclusion that acetate as used in conventional regular hemodialysis does not have a cardiodepressant action. The reported benefits of bicarbonate dialysis therefore involve other factors.

The effects of chronic oral cimetidine therapy on the cardiovascular system in man

1 The demonstration of histamine (H2) receptors in the cardiovascular system in man and the widespread use of the specific H2 receptor antagonist cimetidine for the treatment of peptic ulcer has necessitated assessment of the cardiovascular effects of this drug during oral therapy in man. 2 Consequently, nineteen patients with a history of peptic ulcer but in symptomatic remission underwent a double-blind crossover trial of oral cimetidine v placebo, each treatment period lasting 4 weeks. No significant difference in various cardiac parameters at rest (heart rate, blood pressure, ECG) or following a maximal treadmill exercise test (time-into-protocol, maximum heart rate and blood pressure) was found between the groups. Similarly, cimetidine produced no change in the incidence of ventricular ectopics or in heart rate on 24 h ambulatory monitoring and had no effect on left ventricular volume or contractility as measured by echocardiography. 3 Thus oral administration of cimetidine in a dose of 400 mg four times daily was associated with no demonstrable cardiovascular changes. In addition, since this dose is thought compatible with cardiovascular H2 receptor blockade this study favours the lack of a physiological role for these receptors in man.

Assessment of prognostic factors in patients undergoing surgery for non-rheumatic mitral regurgitation

Twenty-four patients who had undegone mitral valve surgery for pure non-rheumatic mitral regurgitation were studied non-invasively six months to six years postoperatively. The long-term results of operation were assessed on the basis of clinical history, echocardiography, and treadmill stress testing using a points scoring system. The score so obtained was used to divide the patients into those with a good response to surgery (group 1) and those responding poorly (group 2). The effects on the long-term surgical outcome of several intraoperative and preoperative factors were then analysed both together and separately. A short symptomatic history (less than 1 year), a normal left ventricular end-diastolic volume index (less than or equal to 100 ml per m2), and a large post-ectopic potentiation of KV max (greater than 50 s-1) were found to be favourable prognostic factors when analysed independently. An angiographic ejection fraction less than 0.5 was uniformly associated with a poor outcome, and 71 per cent of patients in atrial fibrillation at the time of operation also responded badly. In those patients with good long-term function, cold potassium cardioplegia was more commonly used than intermittent aortic cross clamping as the means of intraoperative myocardial preservation, though this difference did not reach conventional significance. A standard analysis of variance allowed assessment of length of history, left ventricular end-diastolic volume index, and type of valve prosthesis simultaneously. This indicated that both length of history and left ventricular end-diastolic volume index were highly significant prognostic factors. The use of a Björk-Shiley as opposed to a Starr-Edwards prosthesis also emerged as significantly favouring a good long-term result. The state of the left ventricular myocardium before operation and the type of valve prosthesis used were thus shown to be the prime determinants of surgical outcome in these patients. The optimum time for operation was shown to be within one year of the onset of symptoms, and before the left left ventricular end-diastolic volume index exceeds 100 ml per m2, or the ejection fraction falls to less than 0.5. At such a time, irreversible changes in myocardial function sufficient to negate the beneficial effects of mitral valve surgery have not yet occurred.

Controlled study of 24-hour ambulatory electrocardiographic monitoring in patients with transient neurological symptoms

Sixty unselected patients with transient neurological symptoms underwent 24-hour ambulatory electrocardiographic (ECG) monitoring. Haemodynamically significant arrhythmias were observed in 32% of patients, but in only 3% of an age- and sex-matched control group. Nine patients received specific anti-arrhythmic therapy, which resulted in marked symptomatic improvement in each case. It is argued that 24-hour ECG monitoring is a valuable diagnostic tool in the investigation of transient neurological symptoms.

Thallium-201 myocardial imaging in assessment of results of aortocoronary bypass surgery

Thirty-six patients were assessed by thallium-201 myocardial imaging before and after aortocoronary bypass operations and the results were compared with evaluation based on symptomatic assessment, exercise testing, and electrocardiography. After operation, the majority of patients were free from symptoms or symptomatically improved with increased exercise duration. Perioperative myocardial damage was shown in eight patients and myocardial ischaemia in 15 patients when assessed by thallium imaging during exercise. Thallium imaging proved more sensitive than electrocardiography in the demonstration of perioperative infarction and in the detection of postoperative ischaemia. Exercise electrocardiography may be misleading after aortocoronary bypass operations. Thallium imaging offers a simple, objective evaluation of the results of revascularisation procedures, throws light on the mechanisms of relief of angina by operation, and helps in the assessment of the patient whose progress is unsatisfactory after operation.

A computerised dichromatic earpiece densitometer for the measurement of cardiac output

This study assesses a precalibrated dichromatic earpiece densitometer and microprocessor for the measurement of cardiac output by indocyanine green dye dilution. The measured cardiac output is compared with values of cardiac output simultaneously determined using a cuvette densitometer. The microprocessor computation of cardiac output agreed very closely with the cardiac output determined by manual calculation from the same dye dilution curves (standard deviation +/- 1.47%). The reproducibility of the earpiece densitometer (standard deviation +/- 5.2%) was virtually identical to that of the cuvette densitometer (+/- 5.3%). In a comparison of earpiece and cuvette densitometers for 60 measurements of cardiac output following pulmonary arterial injection of dye and for 50 measurements following femoral venous injection of dye, correlation coefficients were 0.83 and 0.78 and the standard deviations of the differences of simultaneous measurements were 7.2% and 8.3% respectively. The instrument offers an accurate reproducible and relatively noninvasive technique for measuring cardiac output.

Echocardiographic and exercise evaluation of results of mitral valvotomy operations

M-mode echocardiography was performed in 54 patients 1 month to 3 years after mitral valvotomy for dominant mitral stenosis. The mitral valve closure index (MVCI), an index previously shown to correlate well with the calculated mitral valve area, was used to diagnose residual mitral stenosis. Using the equation MVCI = 33 MVC--12, 12 patients (22%) were deemed to have mild, 4 (7%) moderate, and 2 (4%) severe residual stenosis. Repeat cardiac catheterisation confirmed the diagnosis in 7 patients. The postoperative mitral valve closure index correlated significantly with patients' subjective symptoms and objective exercise indices. It was higher in patients in whom the posterior mitral leaflet movement became normal after valvotomy, and was lower in patients in whom the anterior mitral leaflet excursions below 14 mm before operation. The mitral valve closure index is a sensitive index for diagnosing residual mitral stenosis after valvotomy.

The effect of propranolol on thyroid hormones and oxygen consumption in thyrotoxicosis

The possibility that propranolol may exert its beneficial actions in thyrotoxicosis by an effect on thyroid hormone concentrations has been investigated by measuring these and oxygen consumption in a group of thyrotoxic patients before and after treatment with propranolol. Following treatment a significant fall in plasma T3 concentration and oxygen consumption occurred and a direct correlation was found between these two variables. Propranolol may, therefore, exert some of its beneficial effects in thyrotoxicosis by an action on T3 metabolism.

Three-day and ten-day chemotherapy for urinary tract infections in general practice

The length of a course of antibiotic treatment for urinary tract infection varies with the habits of the prescriber. Many patients do not complete a course of treatment once their symptoms have subsided. In uncomplicated urinary tract infection among women seen in general practice a three-day course of amoxycillin was as effective as a 10-day course of the same drug in the same dose. Relief of symptoms was equal in both groups and bacteriuria was eliminated equally successfully in both regimens. There was no significant difference between the two groups in the incidence of side effects from the drugs. The financial saving which could accrue from adopting this therapeutic regimen would be significant.