Heart

Milne, J R; Camm, A J; Ward, D E; Spurrell, R A

doi: 10.1136/hrt.43.1.1pmid: 7356855

Changes in the QT and QTc intervals were studied in 16 patients by atrial pacing at rates of 100, 130, and 150 beats/minute. In all patients the measured QT shortened when the atrial paced rate was increased, but when corrected for heart rate the QTc lengthened. Intravenously administered propranolol produced a bradycardia and a lengthening of the QT interval in 15 of the 16 patients studied. When the QT interval was corrected for heart rate using Bazett's formula the QTc was shortened in 13 patients, unchanged in one, and lengthened in two. However, when the QT interval was measured at identical atrial paced rates the QT of the 15 patients studied was lengthened in 10 and unchanged in five. In none was the QT interval shortened. These results show firstly that Bazett's formula is unsuitable for correction of QT interval changes induced by atrial pacing, and secondly that, though intravenously administered propranolol usally produces a shortening of the QTc, when its effect is assessed directly by using an identical atrial paced rate the QT interval usually lengthens, or may remain unchanged, but never shortens. It is suggested that the formal assessment of drug induced QT interval changes should be made at identical atrial paced rates.

Pritchett, E L; Prystowsky, E N; Benditt, D G; Gallagher, J J

doi: 10.1136/hrt.43.1.7pmid: 7356864

'Dual atrioventricular nodal pathways" were found in five patients who also had the Wolff-Parkinson-White syndrome. All five patients had a re-entrant tachycardia that used the atrioventricular node for conduction in the anterograde direction and an accessory atrioventricular pathway for conduction in the retrograde direction. One of the patients also had a re-entrant tachycardia that originated within the atrium or the atrioventricular node. Dual atrioventricular nodal pathways were identified in three of the five patients during their first electrophysiological study because the effective refractory period of the accessory atrioventricular pathway in the anterograde direction was longer than the effective refractory period of the fast atrioventricular nodal pathway. In the other two patients the dual atrioventricular nodal pathways were found only after operative division of an accessory atrioventricular pathway. Re-entrant tachycardia that uses an accessory pathway may be cured by operative division of the accessory pathway. Tachycardia resulting from re-entry within the atrioventricular node cannot be cured by an operation unless the normal conduction system is divided and a permanent pacemaker implanted. These five patients indicate the importance of determining the aetiology of tachycardia by studying the tachycardia itself and not only the type of atrioventricular conduction present.

Southall, D P; Richards, J; Mitchell, P; Brown, D J; Johnston, P G; Shinebourne, E A

doi: 10.1136/hrt.43.1.14pmid: 7356857

Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2.5 kg. The highest heart rate a minute, measured over nine beats, was 175 +/- 19 (SD). The lowest rates, measured over three, five, and nine beats were 82 +/- 12, 87 +/- 12, and 93 +/- 12, respectively. At their lowest rates 109 infants had sinus bradycardia and 25 had junctional escape rhythms. Thirty-three infants showed changes in P wave configuration with or without pronounced variation in PR interval. Atrial premature beats were present in 19 infants but only one had more than 12 per hour. In a randomly selected subgroup of 71 infants sinus pauses were found in 51 (72%). Five (7%) had electrocardiographic patterns and rhythm disturbances that could not be differentiated from those previously described as complete sinuatrial exit block or sinus arrest, eight (11%) had patterns indistinguishable from 2:1 sinuatrial block, and 23 (32%) had pattern indistinguishable from sinuatrial Wenckebach block. This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal.

Southall, D P; Keeton, B R; Leanage, R; Lam, L; Joseph, M C; Anderson, R H; Lincoln, C R; Shinebourne, E A

doi: 10.1136/hrt.43.1.21pmid: 7356858

Gussenhoven, W J; Spitaels, S E; Bom, N; Becker, A E

doi: 10.1136/hrt.43.1.31pmid: 7356859

Daniel, W; Rathsack, P; Walpurger, G; Kahle, A; Gisbertz, R; Schmitz, J; Lichtlen, P R

doi: 10.1136/hrt.43.1.38pmid: 7356860

M-mode echocardiographic studies were performed in 11 patients, most of them adults, with Ebstein's anomaly of the tricuspid valve, proven by cardiac catheterisation. Simultaneous recordings of the tricuspid and mitral valves were obtained in all cases, the transducer position being outside the left midclavicular line in seven patients. Tricuspid valve closure followed mitral valve closure in all cases, with an interval ranging between 0.04 and 0.14 s. Since, in more than 8500 routine echocardiographic studies a valve closure interval between 0.09 and 0.12 s was seen in only one patient without Ebstein's anomaly, an interval of 0.065 s or more should be regarded as diagnostic of Ebstein's disease; however, an interval shorter than 0.065 s does not exclude this diagnosis. In all patients a paradoxical septal movement was found. Two patients showed an atypical three-peaked diastolic pattern of movement of the anterior tricuspid leaflet and one patient also showed mitral valve prolapse. Pathological tricuspid valve closure delay, shown by echocardiography, makes it possible to diagnose Ebstein's anomaly in many cases without resort to cardiac catheterisation which has a relatively high risk in this disease.

Hagemeijer, F; Verbaan, C J; Sonke, P C; De Rooij, C H

doi: 10.1136/hrt.43.1.45pmid: 7356861

In four patients with rupture of the free wall of the left ventricle, the diagnosis was made at the bedside using a portable cross-sectional echocardiograph; this was confirmed at necropsy in two patients and by paracentesis in the other two. Weak ventricular contractions were seen after each QRS complex of the electrocardiogram, contradicting a widespread belief that cardiac rupture immediately produces electromechanical dissociation. In one patient aspiration of 100 ml blood from the pericardium allowed resumption of cardiac pump function; this patient survived for three days but was allowed to die because of cerebral damage sustained during resuscitation.

Wainwright, R J; Maisey, M N; Edwards, A C; Sowton, E

doi: 10.1136/hrt.43.1.47pmid: 7356862

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.

Wainwright, R J; Brennand-Roper, D A; Maisey, M N; Sowton, E

doi: 10.1136/hrt.43.1.56pmid: 6965585

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.

McLaren, M J; Lachman, A S; Pocock, W A; Barlow, J B

doi: 10.1136/hrt.43.1.67pmid: 7356863

Normal auscultatory findings were studied during a heart survey in which 12 050 Black schoolchildren, aged 2 to 18 years, were examined by cardiologists. Physiological third heart sounds were detected in 96 per cent of children, innocent systolic murmurs in 72 per cent, and innocent mid-diastolic murmurs in 0.27 per cent. The term 'innocent systolic murmur" was used for vibratory systolic murmurs (70%) and pulmonary ejection systolic murmurs (4.2%) but distinct separation of these two murmurs was often difficult. Vibratory systolic murmurs were present throughout the age range. Important features in differentiating innocent systolic murmurs from those caused by mild organic heart disease included the intonation, site of maximal intensity, timing in systole, and behaviour with postural change. Innocent mid-diastolic murmurs are short murmurs occurring immediately after the third heart sound in children, with no supportive evidence of organic heart disease.