Time equals myocardium: are we in time?

OBJECTIVE: To determine the door to thrombolysis time of patients who presented to the Adult Priority Care Facility of the Eric Williams Medical Sciences Complex from February 1-May 31, 2008. METHOD: The patients who presented to the Adult Priority Care Facility of the Eric Williams Medical Sciences Complex with cardiac type chest pain and ST segment elevation that met the international criteria and had positive troponin test were interviewed and their notes reviewed to obtain the relevant information. RESULTS: Fifty-one patients were treated with ST segment elevation myocardial infarctions; 78.4% were thrombolysed. Patients were: 59.75 years old, 68.6% male and 66.7% were of East Indian extraction The average time to thrombolysis was 5 hours and 31 minutes from the onset of chest pain. The average door to thrombolysis time was 2 hours and 7 minutes with 20% of patients having a door to thrombolysis time of 30 minutes. The time to thrombolysis from the onset of chest pain and the door to thrombolysis times were adversely affected by the health facility to which the patient first presented CONCLUSION: The majority of patients presented within the thrombolysis window. Early recognition of symptoms of myocardial infarction and arrival at a healthcare facility is not being achieved by the majority of patients. The systems that are responsible for the transport, triage and treatment of patients who present with chest pain are inadequate and require urgent review and overhaul to achieve the goals outlined by the American Heart Association and the American College of Cardiologist.

Evaluation of left ventricular mass and diastolic function in the treatment of hypertension with beta blockers [abstract]

Arterial hypertension is associated with left ventricular hypertrophy (LVH), and LVH increases the risk for cardiovascular morbidity and mortality. Selected antihypertensive agents have been shown to reverse LVH. In this study, the effects of celiprolol, a selective á1 blocker with partial agonist activity on á2 receptors and propranolol, a non-selective á-blocker, on blood pressure, left ventricular mass of diastolic function were compared. In a prospective study, twenty-nine patients with mild to moderate hypertension were randomly allocated to treatment with either celiprolol or propranolol for twelve weeks, after a three-week drug washout period. Cross-sectional doppler echocardiography was performed for the measurement of left ventricular mass and pulse doppler studies done for evaluation of left ventricular diastolic function. At the end of the study, both celiprolol and propranolol significantly reduced the diastolic blood pressure, while only celiprolol significantly reduced the systolic blood pressure. In the celiprolol group, there was a greater decrease in the left ventricular mass (7.9 percent) compared to the propranolol group (0.3 percent), but this was not significant. Doppler studies established that propranolol caused no significant change in the E/A ratio, while celiprolol caused a significant increase in the E/A ratio (p= 0.01). Propranolol increased the deceleration time (DT) (p= 0.001), while celiprolol decreased the isovolumetric relaxation time (IVRT) (p= 0.002) and increased the pulmonary venous A wave width (P= 0.02). In conclusion, short-term treatment with celiprolol demonstrated a trend towards decreasing the left ventricular mass, and caused significant improvement in left ventricular diastolic function, while propranolol did not. This may be due to the observation that celiprolol reduces total peripheral resistance by vasodilation. Treatment with celiprolol over a longer interval may result in significant reduction of left ventricular mass. (AU)

Systolic left ventricular dysfunction detected by echocardiography: demographics and aetiology - abstract

The aim of this retrospective study was to determine the demographic features and causes of heart failure in patients presenting a tertiary care institution: 65 patients aged >16 years with an ejection fraction (EF) < 40 percent, undergoing echocardiography during a two-year period, 1992-94, were included in the study. The mean age was 60 ñ 12 years, 68 percent were male, 50 percent and 42 percent were African and East Indian, respectively. The prevalence of diabetes and hypertension was 40 percent and 45.3 percent respectively. The majority of patients were in NYHA class II or III. The mean left ventricular ejection fraction (LVEF) was 29.7 ñ 8.6 percent. There was no correlation between NYHA class and LVEF at initial presentation. The underlying causes of heart failure were coronary artery disease (CAD) (42 percent), idiopathic dilated cardiomyopathy (10.9 percent), hypertensive heart disease (9.4 percent), alcohol related dilated cardiomyopathy (7.8 percent), valvular heart disease (7.8 percent), myocarditis (1.6 percent) and hypertrophic cardiomyopathy (1.6 percent). The dominant primary cause could not be determined in 18.8 percent. LVEF was similarly depressed in the two major ethnic groups and in the ischaemic and non-ischemic cardiomyopathy groups. We concluded that CAD was the most common cause of LV systolic dsyfunction and that LVEF was not related to ethnicity, aetiology or severity of symptoms. (AU)

Is cardiac catheterization being appropriately utilized in Trinidad and Tobago?

Coronary angiography is an expensive technology which has recently become available in Trinidad and Tobago. Established methods have not so far been proposed to monitor the appropriateness of its utilization. We hypothesized that a frequency of normal results comprising greater than 25 percent of the population undergoing coronary angiography should prompt a review of policy with a view to improving resource utilization. This is consistent with the American Heart Association's benchmark figure of 25 percent set for mature laboratories operating in the United States. We therefore retrospectively reviewed all catheterization records of patients undergoing cardiac catheterization at the Eric Williams Medical Sciences Complex during its first three years of operation (1993-1995). Of a total of 785 patients undergoing procedures, 453 had coronary angiography. The number of studies per year increased from 96 in 1993, to 190 in 1994 and 167 in 1995. Thirty-one percent of patients were reported to have normal coronary arteries in the first year of operation. However, this fell to 22 per cent in 1994 and 21 percent in 1995. The first year's statistics are believed to represent a cautious initial referring practice and a learning curve. Second and third year statistics confirm an appropriate pattern of cost-efficient utilization of cardiac catheterization resources at this institution. We propose that the frequency of the finding of normal coronary angiograms is a valid indicator of the appropriateness of resource utilization, which should be voluntarily reported by catheterization laboratories throughout the region (AU)

Sweet taste transduction in hamster: sweeteners and cyclic nucleotides depolarize taste cells by reducing a K+ current.

1. The gigaseal voltage-clamp technique was used to record responses of hamster taste receptor cells to synthetic sweeteners and cyclic nucleotides. Voltage-dependent currents and steady-state currents were monitored during bath exchanges of saccharin, two high-potency sweeteners, 8-chlorophenylthio-adenosine 3',5'-cyclic monophosphate (8cpt-cAMP), and dibutyryl-guanosine 3',5'-cyclic monophosphate (db-cGMP). 2. Of the 237 fungiform taste cells studied, only one in eight was sweet responsive. Outward currents, both voltage-dependent and resting, were reduced by all of the sweeteners tested in sweet-responsive taste cells, whereas these currents were unaffected by sweeteners in sweet-unresponsive taste cells. 3. In every sweet-responsive cell tested, 8cpt-cAMP and db-cGMP mimicked the response to the sweeteners, but neither nucleotide elicited responses in sweet-unresponsive cells. Thus there was a one-to-one correlation between sweet responsivity and cyclic nucleotide responsivity. 4. Sweet responses showed cross adaptation with cyclic nucleotide responses. This indicates that the same ion channel is modulated by sweeteners and cyclic nucleotides. 5. The sweetener- and cyclic nucleotide-blocked current had an apparent reversal potential of -50 mV, which was close to the potassium reversal potential in these experiments. In addition, there was no effect of sweeteners and cyclic nucleotides in the presence of the K+ channel blocker tetraethylammonium bromide (TEA). These data suggest that block of a resting, TEA-sensitive K+ current is the final common step leading to taste cell depolarization during sweet transduction. 6. These data, together with data from a previous study (Cummings et al. 1993), suggest that both synthetic sweeteners and sucrose utilize second-messenger pathways that block a resting K+ conductance to depolarize the taste cell membrane.

Coronary artery bypass surgery at the Eric Williams Medical Sciences Complex: clinical profile and outcome - abstract

Coronary artery bypass grafting surgery (CABG) has been recently performed at the Eric Williams Medical Sciences Complex, for the management of patients with coronary artery disease (CAD). This is a review of the joint experience of the Eric WIlliams Medical Sciences Complex/Caribbean Heart Care Venture. Forty-one patients had CABG between November, 1993 and October, 1994. Their ages ranged from 39 to 73 years with mean age 56 years; 28 patients (83 per cent) were male and 7 (17 per cent) were female. Twenty patients (49 per cent) were hypertensive, 16 (39 per cent) were diabetic, 5 had mild pre-operative impairment of renal function, 1 had had previous bypass surgery in 1984 and pre-operatively most patients were using maximal oral therapy for angina control. The indications for surgery were: left main coronary disease (7 per cent), 3-vessel coronary disease with ejection fraction < 50 per cent (12 per cent), unstable or refractory stable angina due to 2-vessel, 3-vessel or proximal left anterior descending coronary disease with good LV function (80 per cent). Left internal mammary artery grafts were used in 68 per cent of patients and saphenous vein grafts in the rest. The mean stay in hospital post-operatively was 9.6 days. Two patients died, both in the early post-operative period. In two patients, in whom complete revascularization was not possible, mild angina occurred during the post-discharge mobilization period. All other patients have been free of angina since discharge. Complications included early re-operation (day 1) for excessive bleeding from the chest drains (1 patient), aortic dissection requiring repair (1 patient), lobar atelectasis requiring prolonged physiotherapy (4 patients), pneumonia (1 patient), severe transient post-pericardiotomy syndrome (1 patient) and peroneal nerve palsy (1 patient) (AU)

Sweet taste transduction in hamster taste cells: evidence for the role of cyclic nucleotides.

1. Physiological and behavioral responses to artificial sweeteners, natural sweeteners, and cyclic nucleotides were assessed using two techniques. An extracellular "in situ" technique recorded action potentials from fungiform taste buds and the two-bottle preference test measured behavioral preferences for the different sweeteners. 2. Two high-potency sweeteners, NC-00274-01 (NC01) and NC-00044-AA (NCAA), were preferred over water at micromolar concentrations. Saccharin and sucrose were likewise preferred, but at millimolar concentrations. 3. Bursts of action currents were elicited by sucrose at 200 mM, saccharin at 20 mM, and NCAA at 0.1 mM. A concentration-response curve for the high-potency sweetener NC01 revealed a threshold concentration of 1 microM and a saturation concentration of 100 microM. No responses were elicited by aspartame. 4. The responses to different sweeteners adapted rapidly at saturating concentrations. With NC01, adaptation was concentration dependent: at threshold the response adapted very slowly if at all. Adaptation increased with increasing concentration. 5. Membrane-permeant analogues of adenosine 3',5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate mimicked sweeteners in their ability to elicit a response. This occurred with high fidelity: nearly every taste bud that responded to sweeteners also responded to the nucleotides and every sweet-unresponsive taste bud was nucleotide unresponsive. 6. The sweet responses and nucleotide responses occurred in the absence of permeant apical cations and were not enhanced nor diminished by the presence of such cations. Amiloride had no effect on the sweet response.

Apical K+ channels in Necturus taste cells. Modulation by intracellular factors and taste stimuli.

The apically restricted, voltage-dependent K+ conductance of Necturus taste receptor cells was studied using cell-attached, inside-out and outside-out configurations of the patch-clamp recording technique. Patches from the apical membrane typically contained many channels with unitary conductances ranging from 30 to 175 pS in symmetrical K+ solutions. Channel density was so high that unitary currents could be resolved only at negative voltages; at positive voltages patch recordings resembled whole-cell recordings. These multi-channel patches had a small but significant resting conductance that was strongly activated by depolarization. Patch current was highly K+ selective, with a PK/PNa ratio of 28. Patches containing single K+ channels were obtained by allowing the apical membrane to redistribute into the basolateral membrane with time. Two types of K+ channels were observed in isolation. Ca(2+)-dependent channels of large conductance (135-175 pS) were activated in cell-attached patches by strong depolarization, with a half-activation voltage of approximately -10 mV. An ATP-blocked K+ channel of 100 pS was activated in cell-attached patches by weak depolarization, with a half-activation voltage of approximately -47 mV. All apical K+ channels were blocked by the sour taste stimulus citric acid directly applied to outside-out and perfused cell-attached patches. The bitter stimulus quinine also blocked all channels when applied directly by altering channel gating to reduce the open probability. When quinine was applied extracellularly only to the membrane outside the patch pipette and also to inside-out patches, it produced a flickery block. Thus, sour and bitter taste stimuli appear to block the same apical K+ channels via different mechanisms to produce depolarizing receptor potentials.

Ultrastructure of apical specializations of taste cells in the mudpuppy, Necturus maculosus.

The first interaction of taste stimuli with lingual chemoreceptors occurs on the apical membrane of taste cells, since only that portion is exposed to the oral cavity. To gain better insight into this interaction, we examined the pore region of taste buds in Necturus maculosus with scanning electron microscopy (SEM), transmission electron microscopy, and high-voltage electron microscopy. SEM of the pore reveals a patchwork distribution of three morphologically distinct types of apical specializations: long and branched (LB) microvilli, short and unbranched (SU) microvilli, and bundles of stereocilia. As demonstrated in thin and thick sections, LB microvilli are specializations of dark cells, SU microvilli are the apical specializations of light cells, and stereocilia arise from a cell that has the cytoplasmic markers characteristic of light cells. When left in place, the pore mucus completely covers the SU microvilli and partially covers the LB microvilli. However, stereocilia project above the surface and thus are highly exposed to taste stimuli in the oral cavity. These three morphologically distinct types of apical specializations may reveal functional differences among taste cells. The initial interaction between chemical stimulus and taste cell, and possibly chemoreceptor specificity itself, may be influenced by the morphology of the apical ending.