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In a prospective double blind randomised study in 25 consecutive patients a conventional ionic contrast medium (Urografin 370) was compared with the new non-ionic medium iohexol 350 ( Omnipaque ) in left ventriculography and coronary arteriography. In left ventriculography there was a clear patient preference for iohexol by both a visual analogue scale and independent observer assessment. Iohexol also induced a smaller increase in heart rate or decrease in systolic blood pressure than Urografin. In coronary arteriography iohexol resulted in a smaller reduction in heart rate and systolic blood pressure, a smaller maximum increase in RR interval, less prolongation of the PQ and QT intervals and QRS duration, and a lower incidence of induced chest pain, ST segment depression, or T wave deflection. [ABSTRACT FROM PUBLISHER]

The first case of non-operative occlusion of a large coronary to bronchial anastomosis is described. The patient who had severe angina had also a critical stenosis of the anterior descending coronary artery which was successfully dilated by an angioplasty procedure. An occluding balloon was detached in the large distal circumflex coronary artery, beyond all the normal branches. At a repeat catheterisation study seven months later the balloon was intact and in position, and the anastomosis remained occluded. [ABSTRACT FROM PUBLISHER]

A multi-programmable pacemaker (Siemens-Elema Model 668) has been used in the dual demand mode to treat four patients with re-entry tachycardias. In each case excellent clinical control of frequent episodes of tachycardia was obtained over the follow-up time of 12 months. The influence of different pacing rates was investigated. It was found that the time taken to terminate an episode of tachycardia was not consistently related to the pacing rate because of the variable timing of the first pacemaker impulse during the tachycardia cycle. It was concluded that pacing rates should be chosen so that they are fast enough to prevent recurrence of a tachycardia following termination of an episode, and should not be a simple fraction of the tachycardia rate. The possibility of programming hysteresis allows rapid post-tachycardia rates to be obtained temporarily. Dual demand pacing at present offers a completely automatic method of electrical termination of re-entry tachycardias, but is still restricted to patients whose episodes can be interrupted by a single ectopic beat. [ABSTRACT FROM PUBLISHER]

Conversion of atrial fibrillation or flutter is electrical and, if drugs fail to prevent recurrence, low energy His bundle ablation with im- plantation 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 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. [ABSTRACT FROM AUTHOR]

Eight patients with the Siemens Elema ‘Tochylog’ 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. [ABSTRACT FROM AUTHOR]

High energies delivered via standard pacing catheter electrodes produce permanent atrioventricular conduction block and generate high pressures. We investigated the use of lower energies and an active fixation electrode. Ten patients with refractory supraventricular tachycardias (six with paroxysmal atrial fibrillation, three with dual AV nodal pathways, and one with a concealed accessory atrioventricular pathway) were treated. A 6F Vitatron Helifix electrode was positioned lo give the maximum His bundle deflection. Four shocks of only 50 joules each were delivered at 1-minute intervals. Long-term follow-up showed that seven patients (70%) had persistent complete heart block and two had atrial fibrillation with slower ventricular rates. Nine patients (90%) were symptom-free without antiarrhythmic therapy. Permanent pacemakers were implanted in eight patients. There were no complications resulting from the procedure. Transvenous ablation of atrioventricular conduction can be safely achieved using a Vitatron Helifix electrode and much lower energy values than have been previously employed. [ABSTRACT FROM AUTHOR]

The clinical, angiographic, exercise testing, operative, and follow-up data of 26 patients found at angiography to have left main stem coronary artery stenosis, defined as a reduction in the lumen diameter of 50% or more, are reviewed. There was a high incidence of significant proximal stenosis in the branches of the left main stem. No clinical features were found to distinguish patients with left main stem stenosis. All patients were considered for saphenous vein bypass grafting, selection being based upon the severity of symptoms, left ventricular function, and suitability of the coronary vessels for grafting. Two patients died within 24 hours of coronary angiography. Nine patients were operated on with no mortality. There has been one late cardiac death during a mean follow-up time of 13 months. All patients were symptomatically improved with a significant (P less than 0-01) increase in exercise ability postoperatively. Fifteen patients were not operated on. Six of these patients were regarded as operable but surgery was deferred; five have died at a mean time of 7-2 months. Five of the nine patients regarded as inoperable have died at a mean follow-up time of 14-8 months. The five non-surgical survivors remain symptomatic with no significant change in exercise ability. Recently reported surgical and medical series of patients with left main stem stenosis are reviewed. [ABSTRACT FROM AUTHOR]

Although many different beta blockers are now in clinical use, there is very little information concerning their relative efficacy, and it is still not clear what clinical importance should be attached to properties such as positive inotropic stimulation (intrinsic sympathomimetic activity or ISA) and membrane stabilizing action ("local anaesthetic effect" or "quinidine-like effect"). In this report we compare the ability of patients with angina to exercise on a bicycle ergometer while receiving a series of commonly used beta blockers, and attempt to determine the importance of ISA. The investigation is in four parts with the drugs given orally or intravenously: statistical analysis of the results was carried out using standard methods, both parametric and non-parametric (Friedmann analysis of variance, Wilcoxon matched pairs signed ranks test) by two independent statisticians. The relevant properties of drugs included in this paper are summarized in Table I. Laboratory reports using many different animal preparations may differ from this assessment under specific conditions, and the Table is intended only as a guide to the generally accepted properties of these drugs when used clinically. Results for sotalol are included for reference in the first part of this paper but the drug was withdrawn from clinical use and was not studied further. [ABSTRACT FROM PUBLISHER]

Using His bundle electrograms the effect of Verapamil on the specialized conduction system in eleven patients was studied during routine cardiac catheterization. In five patients, the absolute and relative refractory periods of the A-V node, and retrograde conduction through the A-V node was studied using programmed electrical stimulation techniques. Verapamil caused prolongation of anterograde and retrograde A-V nodal conduction times. The effect on anterograde conduction was only partly reversible with Atropine. No significant effect on the remainder of the conduction system was observed. It is concluded that Verapamil has a direct effect on A-V nodal conduction independent of any vagotonic effect. [ABSTRACT FROM PUBLISHER]

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<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 out-patient procedure allowing investigation of re-entry tachycardia under circumstances mimicking daily life. [ABSTRACT FROM PUBLISHER]

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: = −0.73, <0.05 , = −0.65, < 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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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 I was significantly greater than that for group 2 (P<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< 0.001). Both the rest and peak exercise QRS scores correlated weakly but significantly with ejection fraction (P<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 eject ion 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. [ABSTRACT FROM PUBLISHER]

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 11 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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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 sucess of PTCA. A good angiographic result may not translate into a good functional result if revascularization is incomplete. [ABSTRACT FROM PUBLISHER]

In a study of the concept of pacemaker dependence, 86 patients who had permanent ventricular demand ( VVI) pacemakers implanted for more than six months and were in predominantly paced rhythm underwent repeated interruption of pacing both abruptly and after gradual reduction of paced rate. Non-invasive pace slowing was accomplished by timed inhibiting pulses applied to the chest wall. The results identified a small group (A) of patients, 8% of those tested, who consistently failed to develop an adequate escape rhythm and may thus be considered highly pacing dependent. A second group B, 26%, developed an adequate intrinsic rhythm with serial decremental rate inhibition (SDRI) but suffered symptoms with abrupt complete inhibition (ACI). The remaining 66%, group C, developed no symptoms in any test. Analysis of clinical pre-test data showed that syncope, atrioventricular block and a low rate prior to implant, and a long duration of pacing were associated with a higher degree of pacing dependence, but were not reliably predictive. The clinical significance and value of the results are discussed. We conclude that SDRI is a reliable test for the high degree of pacemaker dependence and can be helpful especially in planning a procedure which may involve interruption of pacing. [ABSTRACT FROM PUBLISHER]

Diurnal variation of exercise test responses occurring during symptom-limited treadmill exercise testing was investigated in 45 patients six weeks after myocardial infarction. Each patient was exercised using a Naughton protocol before 8 a.m. and after 6 p.m. on the same day. No complications arose. There was no significant diurnal variation of any of the analysed exercise induced ischaemic abnormalities (angina pectoris or ST segment shift) or of the mean maximal exercise durations and achieved workloads. Mean maximal heart rates and heart rate-systolic blood pressure double products were similar in both tests. ST segment depression occurred in 21 patients and was totally consistent in both tests. An abnormal blood pressure response occurred in 14 patients in the morning test and in 18 patients in the evening test but this discordance did not reach statistical significance. Similarly there was no significant diurnal variation in exercise induced ventricular arrhythmias, although only three of the 11 patients in whom they occurred had this abnormality on both tests. We conclude that in this group of patients, no significant diurnal variation was observed in either exercise induced ischaemic abnormalities or in exercise haemodynamics during symptom-limited exercise tests performed six weeks after myocardial infarction. These data increase the confidence in clinical management decisions based on the results of this test. [ABSTRACT FROM PUBLISHER]

Symptom-limited Naughton and modified Bruce treadmill exercise protocols were compared in 20 patient to assess their ability in detecting additional ischaemic abnormalities six weeks after myocardial infarction. Eleven patients had a result indicating reversible myocardial ischaemia on both tests while the other nine had no ischaemic abnormality during either of the two protocols. The only significant difference between the two protocols was the longer exercise duration resulting from the Naughton protocol (17.3±5.0 vs, 14.8±2.8 mins, P<0.01). The mean maximum heart rates, rate-pressure products and achieved workloads did not differ significantly. We conclude that even though the Naughton protocol resulted in a significantly longer mean maximum exercise duration, the protocols were equally effective in detecting additional ischaemic abnormalities six weeks after myocardial infarction. [ABSTRACT FROM PUBLISHER]

One hundred and forty-nine patients with suspected ischaemic heart disease were evaluated by exercise thallium-201 myocardial scintigraphy (201Tl SMS), single lead exercise electrocardiography, and coronary arteriography. Myocardial distribution of tracer was assessed semi-quantitatively from digital 201Tl scintigrams and compared with tracer distribution in subjects with normal hearts. Fifty-two of 54 (96%) patients with normal coronary arteries had normal myocardial scintigrams whereas three patients had a positive ischaemic exercise electrocardiogram and were scan normal. Conversely, 36 of 95 (38%) patients with coronary artery disease had a positive ischaemic electrocardiogram compared with 94 of 95 (99%) patients who had a positive myocardial scintigram. Disease in specific coronary arteries could be deduced from the topography of myocardial tracer deficit. Disease was predicted correctly in 76 out of 80 (95%) of left anterior descending coronary stenoses, in 48 out of 64 (75%) of right coronary artery stenoses, and in 55 out of 64 (85%) of left circumflex coronary artery stenosis, despite the presence of infarcted myocardium in other territories. Similarly, single vessel disease was predicted correctly in 14 out of 17 (82%) patients and multiple vessel disease in 64 out of 77 (83%) patients. 201Tl SMS with segmental quantitative analysis is a highly sensitive and specific technique in the diagnosis of coronary artery disease and may be useful screening procedure to select patients for further investigation, particularly those with evidence of life-threatening severe left coronary artery disease. [ABSTRACT FROM PUBLISHER]

A patient with refractory paroxysmal atrioventricular nodal re-entrant tachycardia had required direct current cardioversion to terminate attacks on 83 occasions. A dual demand pacemaker was implanted to sense and interrupt attacks of tachycardia automatically. The pacing electrode was positioned in the proximal coronary sinus near to the atrioventricular node; a site from which fixed rate underdrive pacing successfully interrupted attacks throughout a trial period of one week, with a lead left in this position on a temporary basis. Complete control of the arrhythmia was obtained in the six months after pacemaker implantation. [ABSTRACT FROM PUBLISHER]

Exercise thallium-201 myocardial scintigraphy was performed in 23 patients with hypertrophic cardiomyopathy. Eighteen patients presented with chest pain which was a persistent symptom in 11. Selective coronary arteriography was performed in 16 patients and showed normal coronary arteries in 15 and insignificant luminal irregularities in one patient. Eighteen patients had abnormal scintigrams. Three had an abnormal distribution of tracer entirely attributable to asymmetric septal hypertrophy, whereas 15 had discrete tracer uptake defects which could not be explained solely by myocardial hypertrophy. In this latter group of patients three scintigraphic patterns were identified: (1) in 10 patients defects were seen in scintigrams immediately after exercise but not in delayed images obtained four to six hours later. Eight of these patients had chest pain. (2) Four patients had uptake defects seen in both initial and delayed images. One patient had chest pain. (3) In three patients, one of whom had chest pain, tracer defects were seen only in delayed images and were not apparent in the initial scintigrams. Chest pain occurred in eight out of 10 patients with scintigraphic evidence of myocardial ischaemia but was present in only three out of 13 patients with non-ischaemic scintigrams. The value of exercise thallium-201 myocardial imaging as a diagnostic technique in hypertrophic cardiomyopathy appears limited. Scintigraphic evidence of regional myocardial ischaemia in the absence of significant coronary artery disease, however, contributes to an understanding of the mechanism of angina production in patients with hypertrophic cardiomyopathy. [ABSTRACT FROM PUBLISHER]

A study was performed in 13 patients with idiopathic mitral valve prolapse and in 21 control subjects to assess the effect of the cold pressor test on systolic motion of the mitral valve. A significant increase in blood pressure occurred in 10 patients with mitral valve prolapse and in 19 controls after immersion of one hand in ice-cold water. M-mode echocardiographic recordings from the mitral valve were obtained in all patients before, during, and after the cold pressor test, together with simultaneous phonocardiograms in selected patients. Nine out of 10 patients with mitral valve prolapse and a hypertensive response to the cold stimulus showed a significant increase in the depth of mitral valve prolapse during the cold pressor test whereas in three patients with mitral valve prolapse and no hypertensive response the depth of mitral valve prolapse did not change during cold stimulation. Three patients with previously demonstrated mitral valve prolapse had equivocal resting echocardiograms but developed diagnostic evidence of mitral valve prolapse during the cold pressor test. No evidence of mitral valve prolapse was seen in any of the control subjects before, during or after the cold pressor test. In four patients with mitral valve prolapse and a hypertensive response to cold stimulation the systolic click was delayed by the cold pressor test, whereas the time of the systolic click remained constant in the three patients whose blood pressure did not increase. It is concluded that the cold pressor test provides a stimulus sufficient to delay the onset and increase the depth of mitral valve prolapse, thereby enhancing the diagnostic sensitivity of echocardiography in this condition. [ABSTRACT FROM PUBLISHER]

Four patients with cardiac tumours were investigated by gated cardiac blood pool radionuclide imaging and echocardiography. Contrast angiocardiography was performed in three of the cases. Two left atrial tumours were detected by all three techniques. In one of these cases echocardiography alone showed additional mitral valve stenosis, but isotope imaging indicated tumour size more accurately. A large septal mass was detected by all three methods. In this patient echocardiography showed evidence of left ventricular outflow obstruction, confirmed at cardiac catheterisation, but gated isotope imaging provided a more detailed assessment of the abnormal cardiac anatomy. In the fourth case gated isotope imaging detected a large right ventricular tumour which had not been identified by echocardiography. Gated cardiac blood pool isotope imaging is a complementary technique to echocardiography for the non-invasive detection and assessment of cardiac tumours. [ABSTRACT FROM PUBLISHER]

The predictive accuracy of exercise thallium-201 (201Tl) myocardial scintigraphy in the evaluation of aortocoronary bypass graft surgery was assessed in 48 patients undergoing angiographic investigation 15 months (mean time) after myocardial revascularisation. 201Tl scintigrams detected 61 out of 77 (79%) patent grafts but only 21 out of 42 (50%) occluded grafts, though, for grafts supplying non-infarcted myocardium, the predictive accuracy of graft patency and graft occlusion was 85 per cent and 81 per cent, respectively. Stress electrocardiography failed to detect 15 out of 21 patients with scintigraphic evidence of regional myocardial ischaemia. Residual ischaemia in the proximal left anterior descending coronary distribution was commonly detected in 201Tl scintigrams despite a patent, well-functioning left anterior descending graft to the distal coronary segment. Additional residual ischaemia attributable to ungrafted coronary disease was detected by scintigraphy in 32 (67%) patients and most commonly occurred in the distribution of the diagonal branch of the left anterior descending especially in the presence of a patent distal left anterior descending graft. Thus, independent grafts to the diagonal branch of the left anterior descending are recommended at the time of aortocoronary bypass graft surgery. [ABSTRACT FROM PUBLISHER]

Sixty-five patients with angiographically documented coronary artery disease were investigated by thallium-201 (201Tl) scintigraphy to determine the role of the collateral circulation during dynamic exercise. Fifty-three patients had complete proximal occlusion of at least one major coronary artery. One patient had total occlusion of all three major coronary arteries. Sixty-four collateral channels were identified, graded, and compared with corresponding regions of the myocardial scintigram. Tracer uptake was also graded and classified as various degrees of protection from ischaemia. A significant correlation between good collaterals with complete protection and poor or absent collaterals with no protection was noted. Seventeen patients (20 occluded vessels) had total coronary occlusion without myocardial infarction. Collaterals conferred protection in 9/15 occlusions whereas no protection was seen in five occlusions without collaterals. There was no difference in the protective role of homocoronary and heterocoronary collateral vessels. Hypertrophy of the first septal left anterior descending perforator conferred significant protection from ischaemia in contrast to bridging collaterals and ghosting. During exercise the right coronary bed is preferentially protected from ischaemia, in contrast to the left anterior descending territory. This probably reflects the direction of a transmural flow gradient between left and right ventricles during exercise. [ABSTRACT FROM PUBLISHER]

In the left ventriculogram in the right anterior oblique projection the plane of the mitral valve is seen in profile and the papillary muscle shadows are outlined. The distance from the middle of the papillary muscles to the plane of the mitral valve during systole was used to assess the average length of the chordae tendineae, and the area of the papillary muscle shadows was measured as an index of hypertrophy in a series of hearts with mitral valve disease. Valvar mitral stenosis is characterised by slight reduction in the length of chordae tendineae and more hypertrophy of the papillary muscles, while in subvalvar mitral stenosis there is more shortening of the chordae tendineae and less papillary muscle hypertrophy. Valvotomy may lengthen the chordae tendineae in subvalvar mitral stenosis. In rheumatic mitral regurgitation length of chordae tendineae and papillary muscle size were normal. The measurements were not useful in assessing non-rheumatic mitral regurgitation. [ABSTRACT FROM PUBLISHER]

Forty-six patients admitted with acute coronary insufficiency are reviewed. All were investigated by coronary angiography; 4 had normal coronary arteries and are included in this study; the remainder had a distribution of coronary artery disease similar to other angina patients. The clinical and angiographic findings, management, and subsequent course of the other 42 patients are presented. Fourteen patients (33%) in whom rest pain persisted after 48 hours underwent emergency coronary angiography, with 3 deaths; of the surviving 11 who had acute saphenous vein bypass grafting, 2 died at operation and 3 had perioperative myocardial infarctions. Seventeen patients (41%) who initially improved required surgery within 6 months because of symptoms. Eleven patients (26%) were not operated on. It is concluded that acute coronary insufficiency is best managed initially by intensive medical therapy but a high proportion will require surgery later because of disabling angina. Early investigation and surgery are associated with a high mortality and incidence of myocardial infarction. Survivors of surgery are symptomatically improved and there is a low incidence of late infarction and death. [ABSTRACT FROM PUBLISHER]

Seven patients with normal specialized conduction system and three patients with the Wolff-Parkinson-White (WPW) syndrome were studied using programmed stimulation of the heart before and after the administration of intravenous disopyramide. The principal effect of this drug was to prolong the effective refractory period of the atria and ventricles, and to prolong the effective refractory period of the anomalous pathway in the WPW syndrome. In addition, it prolonged the conduction time in the anomalous pathway in the WPW syndrome. These findings suggest that disopyramide would be a useful and safe drug in the management of certain atrial and ventricular arrhythmias and in the management of the Wolff-Parkinson-White syndrome with atrial fibrillation. [ABSTRACT FROM PUBLISHER]

The pre- and postoperative patterns of coronary artery collateral circulation have been studied in 34 patients who had saphenous vein bypass grafting. When the graft remained patent homocoronary collaterals could not be visualized after operation, but new intercoronary anastomoses frequently developed to other diseased arteries. When the graft and the bypassed artery were both obstructed there was a high incidence (5 out of 11) of myocardial infarction despite good preoperative collaterals. [ABSTRACT FROM PUBLISHER]

Twp patients with type B WPW syndrome and reciprocal tachycardias have been studied using intracardiac electrograms and programmed electrical stimulation of the heart. One patient, who had a right-sided accessory pathway giving the surface electrocardiographic appearances of type B WPW syndrome, was shown to have an additional left-sided accessory pathway as occurs in type A WPW syndrome. This concealed left-sided atrioventricular connexion formed the retrograde pathway during reciprocal tachycardia. In the second patient the appearances of type B WPW syndrome were shown to be caused by an accessory pathway between the atrial septum and the right side of the interventricular septum rather than an accessory pathway in the right atrioventricular groove. The significance of these findings when considering surgical interruption of an accessory atrioventricular conduction pathway is discussed. [ABSTRACT FROM PUBLISHER]

Systolic time intervals were measured in 24 patients with acute myocardial infarction and compared to normal values predicted for heart rate and sex. Pulmonary artery pressures were measured in 18 patients and cardiac outputs using the Fick technique in 10 patients. In all patients the QS2 interval (total electromechanical systole) was short during the acute episode. This shortening in the QS2 interval was due primarily to a reduction in left ventricular ejection time (r=0·71; P<0·001) with no change in the pre-ejection period. The mean deviation from normal of the QS2 interval was 27 ± 3·6 msec in patients with an uncomplicated clinical course and 52 ± 4·7 msec in patients with a complicated course, the difference being significant at the 1% level. Those patients with the highest pulmonary artery diastolic pressure tended to have the shortest QS2 intervals (r=−0·58; P<0·01). There was no relationship between stroke volume and the deviations in the QS2 and left ventricular ejection time intervals from normal. The implication of these findings is discussed. [ABSTRACT FROM PUBLISHER]

The function of implanted pacemakers was assessed at a special pacemaker clinic at intervals of three to six months. Measurements of the basic discharge rate of the pacemaker were made and the waveform was recovered from skin electrodes and displayed on an oscilloscope screen. The impulse was photographed from the screen and subsequent waveform analysis was carried out. Reproducible results were obtained for measurements of peak amplitude and impulse duration provided unipolar electrodes were in use and the patients were studied in the same position. The range of variation of the measurements during the lifetime of different models of normally functioning pacemakers is given. Test measurements taken before failing pacemakers were removed have been correlated with the subsequently established cause of failure and the waveform analysis test has been shown to be clinically reliable. The value of the test depended largely upon the type of pacemaker but it correlated well with rate changes in pacemakers designed to slow as battery exhaustion developed. The clinical value of waveform analysis tests is in the diagnosis of exit block, electrode failure, and premature battery exhaustion and in determining the optimum time for pacemaker replacements. The indications for replacement of pacemakers at the National Heart Hospital are given. Initial experience with an automatic analyser with three types of pacemaker shows that rapid measurements of the waveform parameters can be achieved with accuracy. [ABSTRACT FROM PUBLISHER]

Recirculation times measured from Cardio Green dye curves at rest and during exercise in four normal subjects and 12 patients with heart disease were inversely related to cardiac output. During gaseous techniques for estimation of cardiac output, sampling should be performed within 15 sec at rest and 10 sec during exercise, to avoid errors due to recirculation. [ABSTRACT FROM PUBLISHER]