Graham Leech

Risk of patent foramen ovale for thromboembolic events in all age groups

The association between a patent foramen ovale (PFO) and thromboembolic events in young patients has been reported. Autopsy data suggest that a PFO may be present in 20 to 35% of the population. To further assess the role of a PFO in patients with possible thromboembolic events, precordial and transesophageal contrast echocardiography was performed in 104 consecutive patients (age range 16 to 84 years) presenting with a stroke, transient ischemic attack or peripheral artery embolus (group I). These patients were compared with 94 consecutive patients (age range 23 to 82 years) undergoing transesophageal echocardiography for other reasons (group II). A PFO was found in 22 patients; 9 of 35 (26%) with an event but no risk factor (group Ia), 10 of 69 (14%) with an event but a recognized risk factor (group Ib), and 3 of 94 control patients (3.2%) (group II) (group Ia vs II: relative odds 10:1, p less than 0.001; group Ib vs II: relative odds 5:1, p less than 0.01; and group Ia vs Ib: p = not significant). The detection of a PFO was not related to age. The relatively low prevalence of a PFO in this study may reflect patient selection, but other explanations include: (1) Transesophageal contrast echocardiography may be relatively insensitive for its detection; (2) the prevalence in the general population may have been overestimated; and (3) most PFOs are very small, clinically insignificant and undetectable with this technique.(ABSTRACT TRUNCATED AT 250 WORDS)

The aetiology and course of isolated severe aortic regurgitation: a clinical, pathological, and echocardiographic study.

Seventy two consecutive patients with severe isolated aortic regurgitation were evaluated by preoperative echocardiographic and angiographic assessment of the aortic root. Biopsy specimens of the aortic wall were taken at operation. Two major groups of patients were found: those with cusp derangement but normal aortic roots and those with normal cusps but dilated aortic roots. Of the 42 cases of abnormal cusps, 20 were rheumatic, 15 were infective, and six were bicuspid. One patient had a tear in an otherwise normal cusp. Of the 30 cases of abnormal roots but normal cusps, six had inflammatory changes (syphilis, Reiters disease, giant cell aortitis) and 24 had root dilatation caused by non-inflammatory destruction of elastic laminae. Echocardiographic measurement of the aorta at the level of the top of the commissures predicted the findings at pathology. In 37 of 39 patients with cusp disease the measurement was less than 37 mm. In 27 of 33 patients with root disease the measurement was greater than or equal to 37 mm. This difference was statistically significant. There was no difference in the sizes of the prosthesis used in each group, suggesting that it was the diameter of the junction of the aorta with the sinuses rather than the junction of the sinuses with the ventricle that was important in aortic regurgitation. Clinical progression in patients with non-inflammatory aortic root disease is slower than in patients with infective disease but faster than in those with rheumatic cusp disease.

Transesophageal contrast echocardiography and color flow mapping: methods of choice for the detection of shunts at the atrial level?

The detection of shunts at the atrial level is important, and a reliable means of diagnosis is required. Precordial contrast echocardiography is usually performed to detect such shunts. To investigate the advantages of transesophageal echocardiographic techniques, we studied 167 consecutive patients with both precordial and transesophageal echocardiography, using two-dimensional imaging with contrast techniques (with and without a Valsalva maneuver) and color flow mapping. A patent foramen ovale was diagnosed in 31 patients, an atrial septal defect in 11 (7 with bidirectional shunts), and a pulmonary arteriovenous fistula in 3 patients. All right-to-left shunts were detected with transesophageal contrast echocardiography. With these results used as the gold standard, the sensitivity of combined precordial techniques was 37% and that of transesophageal color flow mapping 46%. All left-to-right shunts were detected by transesophageal color flow mapping. With these results used as the gold standard, the sensitivities of both precordial color flow mapping and a transesophageal negative right atrial contrast study were 27%. We conclude that transesophageal contrast echocardiography is the echocardiographic method of choice for the detection of a right-to-left shunt at the atrial level, which cannot be excluded by negative results on precordial study or on transesophageal color flow map study. A left-to-right shunt at this level is best detected by transesophageal color flow mapping.

Complete right bundle-branch block: echophonocardiographic study of first heart sound and right ventricular contraction times.

High speed enchocardiograms of the mitral, tricuspid, and pulmonary valves were recorded with a simultaneous electrocardiogram and phonocardiogram in 20 patients with complete right bundle-branch block and in 67 normal subjects. Late opening of the pulmonary valve indicating late right ventricular ejection was found in all patients. In 8 patients with wide splitting of the first heart sound the late ejection was related mainly to delay in tricuspid valve closure, suggesting a late onset of the right ventricular pressure pulse. In 10 patients with a single first heart sound the delayed ejection was associated with a long interval between tricuspid valve closure and pulmonary valve opening, suggesting a slow rising right ventricular pressure pulse; 3 of these patients also had late tricuspid valve closure but the tricuspid component of the first sound was absent. Late onset of pressure rise is thought to result from block in the main right bundle-branch, and a slow rising pulse from block in the distal Purkinje network. These findings explain the conflicting results in previous studies of the first heart sound and right ventricular pressure pulse in patients with right bundle-branch block, and may have prognostic significance.

Limitations of transoesophageal echocardiography in patients with focal cerebral ischaemic events.

OBJECTIVE--To investigate the detection rate of cardiac sources of embolism by transoesophageal echocardiography in patients with focal cerebral ischaemic events and to relate the echocardiographic findings to other clinical findings. DESIGN--Prospective study with blinded analysis of the echocardiographic data and subsequent comparison with the other clinical findings. SETTING--Regional cardiothoracic unit based in a teaching hospital. PATIENTS--131 consecutive patients with focal ischaemic cerebral events (49 with a transient ischaemic attack, 77 with a cerebrovascular accident, and five with a retinal arterial embolus) referred for echocardiography. INTERVENTIONS--Full M mode, cross sectional, Doppler, and contrast echocardiography by both the precordial and transoesophageal techniques. RESULTS--Precordial echocardiography detected a cardiac abnormality in 72 patients. Transoesophageal echocardiography confirmed all the precordial findings (except left ventricular hypertrophy, which at present cannot be defined with this technique) and detected other abnormalities in a further 20 patients (18 with potential right-to-left shunts and two with valve vegetations). It also showed spontaneous contrast echoes in 27 of 28 patients with a large left atrium and showed atrial thrombus in three. Cardiac abnormalities were clinically detected in 53 patients, all of which were confirmed or documented by echocardiography. In the 78 patients with no clinically detectable cardiac abnormality six had mitral valve prolapse and one had a regional wall motion defect (identified by precordial echocardiography) and 17 had potential right-to-left shunts (11 of which were identified only by transoesophageal echocardiography). CONCLUSIONS--Transoesophageal echocardiography is more sensitive than precordial echocardiography in detecting potential sources of embolism in these patients. However, except for the detection of a potential right-to-left shunt, the yield in patients with no cardiac abnormality is low. Moreover, the abnormalities detected in those with previously detected cardiac disease merely confirm the clinical diagnosis. Patients with left atrial spontaneous contrast echoes may benefit from anticoagulation but this requires further study. Until more data are available on this feature and on the role of potential right-to-left shunts in this population, the contribution of echocardiography, precordial or transoesophageal, remains limited.

Significance of complete right bundle-branch block when an isolated finding. An echocardiographic study.

Twenty-seven patients with complete right bundle-branch block as the only abnormal finding were studied using high speed M-mode echocardiography to determine the effect of the electrical delay on the mechanical events of right ventricular systole. Pulmonary valve opening (PVOm) was delayed in all cases. In some the delay was mainly between mitral valve closure (MVC) and tricuspid valve closure (TVC), and this was designated proximal block. In the others the main delay was between tricuspid valve closure and pulmonary valve opening and this was designated distal block. The patients were divided into those with proximal and those with distal block by calculating the ratio TVC-PVOm/MVC-TVC. Twelve out of 13 of those with distal delay but only one out of 14 of those with proximal delay had episodes of syncope or near syncope. These results are consistent with previous theories about the pathophysiology of right bundle-branch block. Echocardiography may offer a non-invasive method to estimate the prognosis in isolated right bundle-branch block.

Factors responsible for normal splitting of first heart sound. High-speed echophonocardiographic study of valve movement.

Echocardiographic studies have confirmed that normal splitting of the first heart sound is a result of mitral valve closure preceding tricuspid valve closure. This fits in with contraction of the left ventricle before the right, but the width of splitting is usually greater than would be expected from the known ventricular asynchrony. The importance of atrial systole, which initiates closure of the atrioventricular valves, has not been considered. In this study of 67 normal subjects, high-speed echophonocardiograms were recorded and the timing of mitral and tricuspid valve closure was related to the PR interval and the beginning of left and right ventricular ejection. The timing of mitral valve closure was strongly influenced by the PR interval; in patients with a long PR interval the valve leaflets were nearly apposed by atrial systole and closure was completed early after the Q wave on the electrocardiogram, while with a short PR interval the leaflets were still widely separated at the time of ventricular activation and closure was completed later. The timing of tricuspid closure was affected similarly but less strongly, and even when the PR interval was so long that mitral closure was complete before the onset of left ventricular systole, tricuspid closure occurred up to 48 ms later. The mean interval between mitral and tricuspid closure was 34 ms. Thus mitral closure was effected nearer the onset of left ventricular systole than was tricuspid closure in relation to the onset of right ventricular systole, and this accounts for the surprising width of splitting of the first sound. Variations in splitting of the first sound were mainly the result of variations in the timing of tricuspid rather than of mitral closure. When tricuspid closure was delayed, so was pulmonary valve opening, suggesting that the cause was delay in the onset of right ventricular systole or a slower rate of pressure development in the right ventricle.

Transoesophageal echocardiography in the diagnosis of paradoxical embolism

Two patients with systemic embolism were studied with transoesophageal contrast echocardiography which demonstrated its probable paradoxical nature. In both cases paradoxical embolism was associated with pulmonary embolism. Precordial contrast echocardiography demonstrated a right-to-left shunt in one patient but was unable to demonstrate a shunt in the second. Transoesophageal echocardiography suggested that the shunt was across a patent foramen oval in both cases and revealed large thrombi in the pulmonary arteries in one. When precordial contrast echocardiography reveals a right-to-left shunt or when it is technically inadequate in patients suspected of having one, transoesophageal contrast echocardiography can demonstrate the nature of the shunt and is an alternative to cardiac catheterisation techniques. In addition, it can reveal large thrombi in the pulmonary arteries.

Changes in echocardiographic left ventricular minor axis dimensions during exercise in patients with aortic stenosis.

Twelve patients with aortic stenosis (gradient 62 (25) mm Hg), and six normal subjects were examined using M mode echocardiography before and during submaximal bicycle exercise. Normal subjects showed a progressive fall in the end systolic minor axis dimension of the left ventricle and a rise in end diastolic dimension, giving an increase in stroke dimension and shortening fraction of 45% and 37% respectively at peak exercise. Patients with aortic stenosis showed no consistent alteration in either end systolic or end diastolic dimension, and consequently stroke dimension was unchanged during exercise. None of the patients with an abnormal exercise response had evidence of left ventricular failure at rest, and all but one completed the exercise protocol without undue dyspnoea. Non-invasive exercise testing in patients with aortic stenosis may detect abnormalities of left heart function which are not apparent at rest. These abnormalities may provide early evidence either of severe aortic stenosis or of incipient left ventricular failure.

Comparison of cinefluoroscopy and M mode echocardiography for detecting aortic valve calcification. Correlation with severity of stenosis of non-rheumatic aetiology.

The density of aortic valve calcification was estimated using cinefluoroscopy and M mode echocardiography in 86 patients with pure aortic stenosis. The results were compared with the degree of outflow obstruction measured haemodynamically. Cinefluoroscopic estimates of aortic valve calcification correlated well with the measured aortic valve gradient whereas echocardiographic results were less accurate. Echocardiography gave accurate information about the distribution of calcium within the cusps, but this was not of value in predicting the degree of obstruction. The amount of calcium in the aortic valve as assessed by simple cinefluoroscopy is a useful guide to the severity of aortic stenosis in patients in the middle and older age groups.