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Biomedical subjects

E Sowton

Publications and source records attributed to E Sowton.

At least 55 records · Page 3Linked to original sources
PubMed1988

Physiological variation in the termination window of re-entry tachycardia studied by non-invasive programmed stimulation.

In seven patients with re-entry tachycardias and the implanted antitachycardia device Tachylog (Siemens Elema, Sweden) the variation in the termination window related to posture and exertion was investigated. The investigations were performed on an outpatient basis utilizing the interactive pacing mode of the implanted unit. Six patients had supraventricular tachycardia and one patient had exercise-induced ventricular tachycardia. In all patients, double ventricular stimuli were necessary for tachycardia control. In the patients with supraventricular tachycardia, the termination window decreased significantly in the erect position (-46.5%, P less than 0.001) and in two patients it completely disappeared. Two patients could be studied during exercise. In one patient, exertion caused the termination window to shrink to 63% of its duration standing still, whereas in the other patient it widened to twice its value in the erect position. In the patient with ventricular tachycardia, whom we could study erect only, additional exercise caused the termination window to shrink on average 16.5%. These findings demonstrate that the termination window of re-entry tachycardia varies considerably with posture and exercise. This has important implications for the design of antitachycardia algorithms which will be reliably effective during daily life. Repeated non-invasive stimulation studies can be performed as an outpatient procedure allowing investigation of re-entry tachycardia under circumstances mimicking daily life.

Adolescent↗
PubMed1987

Contrast perfusion echocardiography: distribution and reproducibility of myocardial contrast enhancement in coronary artery disease.

A qualitative assessment was undertaken of the echocardiographic distribution of myocardial contrast enhancement after selective intracoronary injections of 2 ml of hand-agitated Urografin solution. The reproducibility and duration of contrast enhancement has also been examined. Forty-five contrast injections were given, 36 into the left and 6 into the right coronary arteries and 3 into bypass grafts of 28 patients undergoing diagnostic arteriography. Myocardial contrast enhancement occurred in 91% of cases. Although contrast enhancement appeared within the expected area of distribution of the artery infused, in no case was enhancement homogeneous. In 4 patients (1 of whom had undergone coronary bypass surgery), contrast enhancement also appeared in areas remote from the expected perfusion territory, in each case due to well established collateral supply seen angiographically. The contrast effect persisted for 71 +/- 26 seconds. Repeat injection in 5 patients (using identical echocardiographic windows) confirmed the reproducibility of the technique. No patient had symptoms related to the injections, although transient left ventricular wall motion abnormalities were observed in 3 cases. High-grade coronary stenoses did not affect distribution of myocardial contrast enhancement, although coronary occlusions produced well defined deficits. Thus, selective intracoronary injections of hand-agitated echocardiographic contrast medium produce regional myocardial enhancement, which probably reflects the perfusion territory of the artery. The technique is safe and reproducible in human subjects. Nevertheless, because regional enhancement after selective coronary injections is not homogeneous, analysis of enhancement deficits is unlikely to provide a clinically useful means of evaluating the functional significance of coronary stenoses.

Angiography↗
PubMed1987

Contrast perfusion echocardiography: identification of area at risk of dyskinesis during percutaneous transluminal coronary angioplasty.

Two-dimensional contrast perfusion echocardiography was performed in 14 patients who underwent percutaneous transluminal coronary angioplasty to test the efficacy of this new technique for defining the area at risk of dyskinesis during acute coronary occlusion. In nine patients (group A) selective coronary injection of echocontrast medium through the central lumen of the angioplasty catheter was performed immediately before balloon inflation. This produced regional myocardial enhancement that defined the area of dyskinesis after balloon inflation. In five patients (group B) who underwent left coronary angioplasty, echocontrast medium was injected through the introducer catheter positioned in the left main coronary artery during balloon inflation. In each case this produced regional myocardial enhancement remote from the area of dyskinesis. There were no complications related to the intracoronary echocontrast injections, which produced no discernible exacerbation of chest pain or left ventricular contractile dysfunction. These data indicate that selective coronary injection of echocontrast medium defines the perfusion territory of the artery injected and also provides a means of identifying the area at risk of dyskinesis after balloon occlusion of the artery.

Adult↗
PubMed1987

Early percutaneous transluminal coronary angioplasty in the management of unstable angina.

This report describes the results of percutaneous transluminal coronary angioplasty in 56 patients with unstable angina. In each case diagnostic coronary angiography had demonstrated a critical proximal stenosis in a major vessel. The stenosis was successfully dilated without complication in 70% of cases. Angiographic success was reflected by the abolition of symptoms and a nonischaemic predischarge stress test in 82 and 72% of cases, respectively. Importantly, at six months follow-up 69% of these patients remained symptom free though repeat angioplasty had been necessary in 21% of cases. The in-hospital incidence of myocardial infarction and death was 7.1 and 5.4%, respectively, but during the six month follow-up period only one additional complicating event occurred. Results were particularly favourable in patients with single vessel disease, 83% of whom had successful procedures. There was one uncomplicated myocardial infarct in this subgroup but no deaths. These data indicate that percutaneous transluminal coronary angioplasty may be undertaken with relative safety in patients with unstable angina and leads to a substantial improvement in symptoms that is sustained during early follow up. The benefits of this therapeutic approach may be particularly marked in patients with single vessel disease.

Adult↗
PubMed1987

Reversible occlusion of a side branch and the left anterior descending coronary artery following angioplasty.

A 61-year-old man with unstable angina underwent emergency angioplasty of a proximal left anterior descending coronary stenosis. This was successful but a major first septal branch involved in the stenosis was occluded following the procedure. Recovery was uncomplicated, however, without chest pain or other evidence of myocardial infarction. Predischarge treadmill stress testing was negative for ischaemia but two hours afterwards abrupt coronary occlusion required a second emergency angioplasty procedure. Recanalization of the left anterior descending artery was achieved and the first septal branch was shown to be fully patent. Spasm probably accounted for the side branch occlusion which complicated the first procedure but the mechanism of the abrupt coronary occlusion following stress-testing is unclear.

Angina, Unstable↗
PubMed1987

Anisoylated plasminogen streptokinase activator complex in acute myocardial infarction: a placebo-controlled arteriographic coronary recanalization study.

Anisoylated plasminogen streptokinase activator complex (APSAC) is a new thrombolytic agent that is of interest because of its ease of administration as an intravenous bolus injection. This report describes the first double-blind, placebo-controlled evaluation of intravenous APSAC for coronary recanalization in acute myocardial infarction. Unequivocal documentation of recanalization was provided by coronary arteriography before and after the drug intervention. Forty patients with acute myocardial infarction underwent coronary arteriography 3.1 +/- 1.2 hours after the onset of symptoms. This demonstrated occlusion of the infarct-related coronary artery in 29 patients who were then randomized to treatment with intravenous APSAC, 30 mg (n = 16), and placebo (n = 13) 3.3 +/- 1.3 hours after the onset of symptoms. Repeat arteriography 90 minutes later demonstrated recanalization of the infarct-related coronary artery in nine patients who had received APSAC compared with only one patient who had received placebo (56 versus 8%, p less than 0.05). The 95% confidence limits for this 48% difference between the groups are 20 to 76%. Arteriography at 3 days showed persistent patency of all recanalized coronary arteries except one (APSAC group) and also showed late recanalization in another four patients, three of whom had received APSAC. In the patients who had a patent infarct-related coronary artery at the initial arteriographic study, patency was maintained throughout the study period regardless of whether the patient was randomized to APSAC (n = 4) or placebo (n = 7). Complications related to APSAC therapy were excessive bruising at the catheterization site in seven patients and minor sensitivity reactions in three.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Exercise testing in the indication and evaluation of pacemaker treatment.

Comparison of different methods of rate responsive' pacing with expected heart rates at the same work load in normals shows that most systems have not matched rate and effort correctly. P-wave driven pacing tends to produce too fast a rate and QT-driven pacing too slow a rate for the work load. Although there are improvements compared with exercise in fixed rate pacing, these are less impressive than expected. There appears negligible benefit from AV synchrony beyond that achieved by rate increase.

Cardiac Pacing, Artificial↗
PubMed1987

Coronary dilator effects of intracoronary nifedipine and isosorbide dinitrate.

Although both nitrates and calcium antagonists may be administered by the intracoronary route, the relative efficacy of these agents and of their combination is unknown. In this study, we investigated the coronary vasodilatory potential of intracoronary nifedipine, isosorbide dinitrate and their combination in patients undergoing routine coronary arteriography. Both normal and diseased segments of coronary arteries were studied. Coronary artery diameters were measured from 35 mm cine film before and after the administration of each drug. Two groups of 10 patients were studied: group I received nifedipine, 0.2 mg, followed by isosorbide dinitrate, 1 mg, group II received isosorbide dinitrate, 1 mg, followed by nifedipine, 0.2 mg. Both agents resulted in significant dilatation of normal and diseased segments of the coronary arteries when injected as the first drug, but neither nifedipine nor isosorbide dinitrate produced significant additional vasodilation when injected as the second drug. The degree of dilatation of both diseased and normal segments produced by either nifedipine or isosorbide dinitrate was similar, suggesting that the dose used, of either drug, produced near maximal coronary vasodilatation. Importantly, drug induced dilatation of stenotic segments was similar to that of normal segments.

Adult↗
PubMed1987

Use of an exercise QRS score and radionuclide left ventricular ejection fraction in assessing prognosis after myocardial infarction.

We have compared the prognostic value of a predischarge post-infarction QRS score derived at rest and at submaximal exercise with ejection fraction measured by gated radionuclide left ventriculography in 65 patients. Seventeen patients died or had heart failure (group 1) and 48 were well or had angina (group 2) six months after infarction. The mean QRS score derived from the resting electrocardiogram for group 1 was significantly greater than that for group 2 (P less than 0.01) but the QRS scores at peak exercise did not differ significantly between the two groups. The mean ejection fraction for group 2 was significantly greater than that for group 1 (P less than 0.001). Both the rest and peak exercise QRS scores correlated weakly but significantly with ejection fraction (P less than 0.001). The QRS score at rest had a greater sensitivity and specificity in predicting cardiac death and heart failure than the QRS score at peak exercise. A sensitivity of 88% was achieved with a resting ejection fraction less than 50% and a resting QRS score greater than 4. At these values the specificities were 58% and 63% respectively. Combining the blood pressure response to exercise with the QRS score and ejection fraction improved the sensitivity of both with no loss of specificity. Therefore, the resting QRS score is comparable to ejection fraction as a predictor of serious cardiac events after infarction and the sensitivity of both may be improved by including an assessment of the blood pressure response to exercise. Because a 12-lead electrocardiogram is cheap and widely available, this QRS score may be used in risk stratification after infarction.

Adult↗
PubMed1987

Arterial blood infusion for myocardial protection during percutaneous transluminal coronary angioplasty.

Much of the potential risk of percutaneous transluminal coronary angioplasty relates to regional myocardial ischaemia during balloon inflation. We have investigated the protective effect of infusing arterial blood through the angioplasty catheter into the distal coronary artery during 60 second balloon inflations. Symptomatic, electrocardiographic and echocardiographic indices of regional ischaemia were monitored during inflations with and without blood infusion. The effect of infusing Hartmann's solution was also evaluated to control for washout effects. Twelve patients were studied. Inflation without blood produced chest pain in eight patients, ST-segment elevation in ten patients and regional wall motion abnormalities in every case. During blood infusion manifestations of ischaemia were either delayed or prevented altogether. Chest pain occurred in only one patient while ST segment elevation and regional wall motion abnormalities occurred in three and four patients, respectively. Infusion of Hartmann's solution, on the other hand, had no significant effect on the development of regional myocardial ischaemia during balloon inflation indicating that delivery of arterial oxygen and not washout of metabolites was responsible for the beneficial effects of blood infusion. These data indicate that distal coronary perfusion with arterial blood during angioplasty reduces regional myocardial ischaemia and has the potential to improve the safety of the technique and to permit more prolonged periods of balloon inflation.

Angina Pectoris↗
PubMed1987

The evolution of myocardial ischaemia during percutaneous transluminal coronary angioplasty.

Balloon inflation during percutaneous transluminal coronary angioplasty is a useful human model of acute coronary occlusion and regional myocardial ischaemia. We assessed the prevalence and duration of ischaemia during successive sixty-second balloon inflations in sixteen patients undergoing routine single vessel angioplasty by continuous six lead electrocardiography and cross-sectional echocardiography. The influence of rate-pressure product on the evolution of ischaemia was also evaluated. ST segment elevation developed in fourteen of the patients within 19 +/- 12 seconds and returned to baseline within 20 +/- 9 seconds of deflation. Reciprocal ST segment depression occurred in four patients, only one of whom had multivessel disease. Wall motion abnormalities on echocardiography occurred in all sixteen patients and were seen significantly earlier than electrocardiographic changes. Thus, dyskinesis developed 15 +/- 5 seconds after balloon inflation and disappeared 13 +/- 3 seconds following balloon deflation. Time to onset of ischaemia by both methods remained constant during successive balloon inflations. Rate pressure product prior to balloon inflation correlated inversely with time to onset of ischaemia detected by either technique: r = -0.73, P less than 0.05 (ECG), r = -0.65, P less than 0.05 (echocardiography). Nevertheless, evidence of ischaemia developed within 30 seconds in all patients regardless of rate-pressure product. This investigation indicates that electrocardiography and cross-sectional echocardiography have similar sensitivity for the detection of acute ischaemia during coronary angioplasty although echocardiographic change is seen significantly earlier. Resting myocardial oxygen consumption, as reflected by rate-pressure product, is an important determinant of time to onset of ischaemia following balloon inflation.

Angioplasty, Balloon↗
PubMed1987

The effects of early coronary patency on the evolution of myocardial infarction: a prospective arteriographic study.

The effects of early spontaneous coronary patency on the evolution of myocardial infarction were evaluated in 41 patients. They had coronary arteriography (mean (SEM)) 3.1 (0.2) hours after the onset of chest pain with repeat studies 90 minutes and three days later. In 12 (29%) patients the infarct related coronary artery was patent at the first arteriogram (group 1). A further 10 patients, nine of whom received thrombolytic treatment, showed early recanalisation of the infarct related coronary artery within 90 minutes of treatment (group 2). In the remainder the infarct related coronary artery was persistently occluded (group 3). Baseline values for infarct location, the sum of ST elevation in all leads, QRS scores, and serum creatine kinase activity did not permit discrimination between the groups. Nevertheless, patterns of ST segment change and enzyme release in group 1 were closely similar to those that occurred in response to thrombolysis in group 2. Thus compared with group 3, groups 1 and 2 showed earlier 50% reduction in the sum of peak ST elevation in all leads and earlier peaking of serum creatine kinase activity. Importantly, creatine kinase release was significantly attenuated in group 1, rising to a peak serum activity (mean (SEM)) of only 1242 (415) IU/1. Analysis of angiographic left ventricular ejection fractions at three days indicated limitation of infarct size in groups 1 and 2 compared with group 3. Mean (SEM) ejection fraction, however, was best preserved in group 1 (62(6)%) and in this group the frequency of non-Q wave infarction was higher than in groups 2 and 3. Thus in patients who present with a patent infarct related coronary artery early during infarction: (a) there is a reduction in the pattern of infarct size as reflected by attenuation of release of creatine kinase, preservation of left ventricular ejection fraction, and a relatively high frequency of non-Q wave infarction; (b) patterns of ST segment change and creatine kinase release resemble those that occur after successful thrombolytic treatment, suggesting that early coronary patency is the result of spontaneous recanalisation of a previously occluded artery.

Adult↗
PubMed1987

An interim report of a double-blind placebo-controlled recanalisation study of anisoylated plasminogen streptokinase activator complex in acute myocardial infarction.

This is an interim report of the initial 36 patients entered into the first double-blind, placebo-controlled invasive arteriographic study of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) for coronary recanalisation in acute myocardial infarction. Coronary arteriography was performed before and 90 minutes after a single intravenous bolus injection of APSAC or placebo given over 2 to 5 minutes. Pretreatment coronary arteriography was performed in 36 patients at a mean time of 189 +/- 75 minutes after the onset of symptoms. 28 patients had occluded infarct-related coronary arteries and were randomised to receive APSAC 30U (n = 15) or placebo (n = 13) by intravenous injection 195 +/- 72 minutes after the onset of symptoms. Coronary arteriography 90 minutes after treatment demonstrated recanalisation of the infarct-related coronary artery in 8 APSAC-treated patients compared with only 1 placebo-treated patient (p less than 0.02). Repeat coronary arteriography 3 days after treatment showed reocclusion in 1 of the 8 APSAC-treated patients and persistent perfusion in the single patient who reperfused on placebo. All patients with patent vessels at pretreatment coronary arteriography (3 APSAC, 5 placebo) remained patent throughout the study period. There were no haemorrhagic complications related to APSAC therapy. These data confirm that APSAC is a safe, effective thrombolytic agent which, when administered by the intravenous route, resulted in a 53% recanalisation rate.

Adult↗
PubMed1986

The acute haemodynamic effects of quinapril, a new non-sulfhydryl angiotensin converting enzyme inhibitor, in patients with severe congestive cardiac failure.

This study investigates the acute haemodynamic effects of Quinapril (CI-906) a new non-sulphydryl angiotensin converting enzyme inhibitor in 15 patients with refractory congestive cardiac failure. There were 14 males and 1 female mean age 59.5 years. After administration of Quinapril there was a significant reduction in mean arterial pressure (MAP) from 93.1 to 79 mmHg, systemic vascular resistance (SVR) from 1887 to 1349 dyn s cm-5 and PCW from 27.3 to 15.3 mmHg. This was accompanied by an increase in CO from 3.7 to 4.71/min, cardiac index (CI) from 1.97 to 2.51/min/m2 and Stroke volume index from 21.1 to 28.7 ml/m2. There was no significant change in heart rate (HR), right atrial pressure (RAP), or pulmonary vascular resistance. The peak effect on pulmonary capillary wedge pressure (PCW) and cardiac output (CO) occurred at 75-120 min after Quinapril administration. The maximum effect on mean arterial pressure (MAP) occurred slightly later at 120-150 min. SVR and CI exhibited 2 periods of peak effects, at 90 and 180 min. This time course is very similar to that observed in studies on the acute effects of Captopril. The significant improvement in haemodynamic measurements acutely, following administration of Quinapril 5 mg orally, suggests that this drug is worthy of further study in the management of patients with refractory congestive cardiac failure, in particular its long term effects.

Adult↗
PubMed1986

Factors predictive of early angiographic and functional success following percutaneous transluminal coronary angioplasty.

Baseline variables in 300 coronary angioplasty procedures were analysed to identify factors predictive of a successful outcome. Separate multivariate analyses distinguished between predictors of primary angiographic success and functional success as determined by the results of predischarge treadmill stress electrocardiography. Three independent predictors of primary angiographic success were identified: number of balloon inflations per procedure, initial stenosis, and operator experience. Of these, the number of balloon inflations per procedure and operator experience were also predictive of functional success, reflecting the dependence of a good functional result on a successful procedure. Other independent predictors of functional success were the severity of the residual stenosis and single vessel coronary artery disease suggesting that adequacy of revascularization is an important determinant of the functional result. These data illustrate the interaction between clinical, angiographic and functional variables in determining the success of PTCA. A good angiographic result may not translate into a good functional result if revascularization is incomplete.

Adult↗
PubMed1986

Antitachycardia pacing: a comparison of burst overdrive, self-searching and adaptive table scanning programs.

Eight patients with the Siemens Elema "Tachylog" generator implanted for management of paroxysmal reentrant tachycardia were studied to assess the safety and efficiency of three antitachycardia programs. The programs investigated were burst overdrive, self-searching, and adaptive table scanning. There were five males and three females aged 19-62 years. Seven had Wolff-Parkinson-White syndrome, and one had dual atrioventricular nodal pathways. Four had right atrial electrodes and four had right ventricular electrodes. Patients were studied lying, standing, and exercising in all three modes, and the appropriate long-term programs were chosen. The generator remained in a program for 1 month, it was interrogated and the memory was read, and then it was reprogrammed to a different antitachycardia mode. Burst overdrive was unsuitable for long-term use in four patients, producing atrial fibrillation in one and ventricular arrhythmias in three. In this group, self-searching and adaptive table scanning were safe and equally effective (mean number of attempts/tachycardia 6.97 and 6.3, respectively). In the four patients in whom all three programs could be used, burst overdrive proved to be most efficient, the mean number of attempts/tachycardia were 2.4 (cf 9.6 and 9.0 for self-searching and adaptive table scanning). Thus, burst overdrive was only suitable for long-term use in 50% of our patients, but when safe it was more efficient than the other two programs, especially in those with narrow termination windows on exercise.

Adult↗
PubMed1986

Strategies for the management of tachyarrhythmias.

Conversion of atrial fibrillation or flutter is electrical and, if drugs fail to prevent recurrence, low energy His bundle ablation with implantation of a rate responsive pacemaker is our routine. For re-entry tachycardia, antitachycardia pacers are often the method of choice. We use bipolar automatically actuated systems exclusively, functioning either as burst overdrive or critically timed stimulation. His bundle, or accessory pathway ablation, is considered a later choice. Ventricular arrhythmias are initially terminated by by Class I agents or cardioversion and then a trial of suppressive drugs used. If this fails, a combination of an antitachycardia pacemaker plus an automatic implantable defibrillator is implanted. Alternative options are ablation of the arrhythmogenic site, endomyocardial stripping, or an encircling ventriculotomy with cardiac transplantation as the final option considered.

Anti-Arrhythmia Agents↗