Noninvasive assessment of left internal mammary artery graft patency using transthoracic echocardiography

BACKGROUND

Cardiac catheterization is the only practical method of assessing internal mammary artery graft patency. A noninvasive method would be useful in patients with recurrence of anginal symptoms after coronary artery bypass graft surgery. We hypothesized that transthoracic echocardiography could provide information on blood velocity and anatomy and therefore has the potential to allow measurement of blood flow.

METHODS AND RESULTS

High-frequency (5 MHz) transthoracic echocardiography was performed on 41 consecutive patients (mean age, 67 +/- 6 years) who had had left internal mammary artery grafts to the left anterior descending coronary artery (LAD) and were undergoing coronary angiography because of recurrence of anginal symptoms. The results were compared with those from 19 patients (mean age, 58 +/- 11 years) in whom an ungrafted left internal mammary artery was assessed and with those from 15 patients (mean age, 61 +/- 12 years) who had angiographically normal coronary arteries in whom the LAD was studied. Doppler velocity profiles of the left internal mammary graft were obtained in 35 of the 41 study patients (81%). In all cases, a biphasic pattern of blood flow was recorded that corresponded to systole and diastole. Two different flow patterns were observed. In 25 patients with a normal graft or moderate (< 70%) stenosis (group A), blood flow velocity was maximal during diastole. This pattern was also seen in the LAD control group. In 10 patients with severe (> 70%) graft stenosis (group B), blood velocity was maximal during systole, and low velocities were recorded during diastole. This pattern was also seen in the ungrafted internal mammary artery control group. The diastolic fraction of the velocity time integrals for group A was 0.77 +/- 0.07 and for group B was 0.27 +/- 0.01 (P < .05). A diastolic velocity time integral fraction < 0.5 predicted severe stenosis with a sensitivity and specificity of 100%. The ratio of systolic-to-diastolic peak velocities for group A was 0.54 +/- 0.26 and for group B was 3.45 +/- 0.74 (P < .05). A systolic-to-diastolic peak velocity ratio > 1 predicted severe stenosis with a sensitivity of 100% and specificity of 85%. Mean graft blood flow was 63 +/- 21 mL/min. There was no significant difference in mean blood flow between any of the patient groups studied.

CONCLUSIONS

High-frequency transthoracic echocardiography allows identification of the left internal mammary grafts and measurement of blood flow. Compared with patent grafts or those with moderate lesions, severe stenoses demonstrated different Doppler velocity patterns. Use of this technique may allow noninvasive detection of significant stenoses of the left internal mammary artery graft.

Mortality and morbidity after mitral valve repair: the importance of left ventricular dysfunction

A retrospective study of 219 consecutive patients who underwent mitral valve repair for mitral regurgitation or mixed mitral valve disease with at least moderate regurgitation was undertaken. The etiology was degenerative in 151 (68.9%) patients, endocarditis in 24 (10.9%), rheumatic in 22 (10.0%), ischemic in 13 (5.9%), congenital in five (2.3%) and cardiomyopathy in two (0.9%). The average age was 64.8 +/- 10.9 years, the average follow up 30.2 +/- 24.1 months. Pre-operatively, 74% were in NYHA functional class III or IV. Left ventricular function was assessed by angiography and echocardiography, and moderate or severe impairment (ejection fraction < or = 40%) was assumed to represent significant left ventricular dysfunction. There were six (2.7%) hospital deaths, four of which were due to left ventricular dysfunction. The seven-year mortality and seven-year combined mortality and morbidity were 14.4% and 37.1% respectively for complications related to left ventricular dysfunction, and 2.5% and 24.2% respectively for unrelated complications. Subgroup analysis showed that five-year mortality and five-year combined mortality and morbidity due to left ventricular dysfunction were significantly worse in patients who had pre-operative left ventricular dysfunction than those who did not: 28.5% vs. 6.1% (p < 0.001) and 52.4% vs. 17.8% (p < 0.001). There was nevertheless a significant incidence of postoperative left ventricular dysfunction in patients with satisfactory preoperative left ventricular function. In this group, five-year mortality and five-year combined mortality and morbidity due to left ventricular dysfunction were higher in patients who were in NYHA class III or IV preoperatively than in those who were not: 11.2% vs. 0% (NS) and 25.9% vs. 0% (p < 0.01) respectively, particularly if they also had early (3-10 days) post-operative left ventricular dysfunction: 20.4% (p < 0.001) and 41.7% (p < 0.001) respectively. Despite preservation of the mitral apparatus, left ventricular dysfunction remains a major cause of mortality and morbidity following mitral valve repair for mitral regurgitation.

Identification of right atrial thrombi using transoesophageal echocardiography

The in vivo diagnosis of right atrial thrombus is difficult by transthoracic echocardiography and it is likely that small thrombi are underdiagnosed using this approach. Transoesophageal echocardiography provides an unobstructed view of cardiac structures and the great vessels. In this report we describe the findings in five patients with right atrial thrombi that illustrate the potential usefulness of transoesophageal echocardiography for both the initial diagnosis and the subsequent management of these patients.

Early complications after dual chamber versus single chamber pacemaker implantation

This study was performed to compare the frequency of early complications after single chamber versus dual chamber permanent pacemaker implantation. Early complication was defined as one occurring in the 6-week period following implantation. We prospectively analyzed consecutive pacemaker implantation from January 1987 to June 1993 at our regional center. All complications were also analyzed for the relationship to operator experience, the venous access route, and the presence of temporary pacing wire at the time of implantation of the permanent pacing system. A total of 2019 new pacemaker units were implanted during this period. 1733 patients (85.8%) received a VVI pacemaker and 286 (14.2%) a DDD unit. Wound infection occurred in 11 (0.6%) VVI patients and 6 (2.1%) DDD patients. Lead displacement occurred in 18 (1%) VVI patients and 15 (5.2%) DDD patients (11 [3.8%] atrial and 4 [1.4%] ventricular). There were 10 (0.6%) pneumothoraces, 9 (0.5%) hematomas requiring drainage, 1 (0.06%) chylocele, and 2 (0.1%) deaths in the VVI group. There were 2 (0.7%) pneumothoraces, 2 (0.7%) hematomas, and no deaths in the DDD group. There was no significant increase in complications for experienced infrequent implanters (< 12 systems per year). In both groups the subclavian approach was associated with a risk of pneumothorax when compared to the cephalic approach. The rate of wound infection was higher in patients who had a temporary pacing wire in place. The use of prophylactic antibiotics does not appear to affect the incidence of wound infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Magnetic resonance imaging planes for the 3-dimensional characterisation of human coronary arteries

We report a magnetic resonance imaging study which developed a consistent hierarchy of imaging planes for examination of the origins, courses and principal branches of the main coronary arteries of prepared human cadaveric hearts. The reference longitudinal axis was chosen between the aortic valve and the apex of the left ventricle. A series of transverse planes then successfully visualised the ostia of the left and right coronary arteries; the left main coronary, its bifurcation, and the left anterior descending artery for a distance 24 mm distal to its origin were clearly distinct in successively posterior sections as was the emergence and course of the right coronary artery. Further sections were derived from an axis that joined the posterior aspects of the left and right coronary artery ostia seen in cross-section, which demonstrated the origins of these arteries. They also traced the circumflex artery 30 mm beyond its point of emergence and demonstrated the course of the right coronary artery between the right ventricle and right atrium. The anatomical identifications were confirmed in selective 3-dimensional reconstructions of the cardiac anatomy around the aortic root and pulmonary artery origin. The orthogonal anatomical arrangements of the left and right coronary artery arterial trees thus permit a consistent set of imaging planes useful for the visualisation of all the major branches in a static heart in vitro. This may offer an approach useful for clinical imaging of human coronary vessels in vivo in the moving heart.

Intraoperative epicardial echocardiography with a miniature high-frequency transducer: imaging techniques and scanning planes

Intraoperative Doppler echocardiography has the potential to provide anatomic and functional information but is hindered by the large size of standard transducers. We describe new scanning planes accessible through the application of a new 5 MHz miniature transducer with imaging, Doppler, and color-flow capability. Epicardial echocardiography was performed in 15 adults undergoing elective coronary artery bypass grafting. Standard parasternal equivalent, subcostal equivalent, aortopulmonary sulcus and aortosuperior vena caval views were obtained. Previously unobtainable apical four-chamber, five-chamber, and long-axis views were possible by positioning the transducer at the apex. The transducer has a broad bandwidth, allowing high-quality imaging at different depths and could be maneuvered laterally, posteriorly, and over the aorta and pulmonary arteries to provide off-axis views. The proximal-mid coronary arteries were imaged on the beating heart with a standoff medium. Transducer miniaturization should expand the role of epicardial ultrasonography in the surgical management of heart disorders.

Identification of coronary artery stenoses and poststenotic blood flow patterns using a miniature high-frequency epicardial transducer

BACKGROUND

Intraoperative epicardial coronary Doppler ultrasound has the potential to provide anatomic and functional information. This technique has been hindered by the large size of standard transducers, but a miniature transducer is available that may fulfill the potential of coronary ultrasound.

METHODS AND RESULTS

Twenty consecutive patients who were undergoing coronary artery bypass grafting were studied and compared with 9 control patients with normal coronary arteries who were undergoing routine mitral valve surgery. A miniature 6.5-MHz transducer was used to image coronary arteries and measure coronary blood flow velocities. Seventeen proximal left anterior descending and 3 right coronary artery stenoses were studied. As defined by coronary angiography (1 to 34 days before surgery), there were 13 severe stenoses (> 70%), 4 moderate stenoses (40% to 70%), 2 minor stenoses (< 40%), and 1 subtotal occlusion. Stenoses were readily identified by ultrasound. Color flow mapping demonstrated laminar flow in normal arteries and nonlaminar flow across moderate and severe stenoses. In the control patients with unobstructed arteries, peak and mean diastolic velocities were 35 +/- 2.1 and 26 +/- 1.9 cm/s with peak and mean systolic velocities of 16 +/- 1.4 and 11 +/- 0.8 cm/s, respectively. Prestenotic flow velocities were not significantly different from normal control values, but a wide range of poststenotic flow disturbances were detected. Analysis of the 20 study patients did not reveal significant differences in poststenotic compared with prestenotic flow. A subgroup analysis of 12 patients with severe left anterior descending coronary artery stenoses was performed, and reversed poststenotic systolic flow was seen in 9. Prestenotic peak and mean systolic velocities were 16.5 +/- 1.7 and 11.9 +/- 1.1 cm/s, respectively, and were significantly altered downstream of the stenoses at -22.7 +/- 17.2 and -15.9 +/- 10.9 cm/s (P < .05 and P < .01, respectively). Reversed systolic flow was seen only distal to severe left anterior descending coronary artery stenoses and did not correlate with retrograde collateral filling as determined by preoperative coronary angiography. Moderate stenoses appeared to increase both systolic and diastolic components of poststenotic flow.

CONCLUSIONS

Epicardial Doppler ultrasound with a miniature transducer identifies coronary stenoses and associated blood flow disturbances. Compared with moderate lesions, severe stenoses demonstrated different poststenotic flow patterns. Intraoperative use of this technique may determine the hemodynamic significance of coronary stenoses.

Profiles of coronary blood flow velocity in patients with aortic stenosis and the effect of valve replacement: a transthoracic echocardiographic study

OBJECTIVE

To report the first non-invasive assessment by transthoracic Doppler echocardiography of coronary blood flow in patients with aortic stenosis and of the effects of valve replacement.

DESIGN

High frequency transthoracic Doppler echocardiography was used to examine resting phasic flow in the left anterior descending coronary artery before and after replacement of the aortic valve in awake, unsedated patients with pure aortic stenosis and normal coronary arteries.

SETTING

A tertiary referral cardiothoracic centre.

METHODS

Eleven patients with pure aortic stenosis and normal coronary arteries (six men, five women, mean (range) age 69 (50-82) years), were studied the day before and 1 week after replacement of the aortic valve. These patients were selected from a cohort of 15 due to ease of imaging of the left anterior descending coronary artery. Seven had a history of angina. Haemodynamics, peak transvalvar aortic gradient, left ventricular mass index, ventricular dimensions, and profiles of coronary flow velocity were measured. Profiles of coronary flow velocity were also measured in a control population of 10 normal subjects (five men, five women, mean (range) age 58 (34-66) years).

RESULTS

The control population showed forward flow throughout systole, but reversed early systolic flow (mean velocity 20.6 (3.6) cm/s) was seen in six patients with aortic stenosis. Only three of these patients had a clinical history of angina. Peak and mean systolic and diastolic forward flow velocities were not significantly different in the control group and in patients with aortic stenosis. The time from the start of systole to the onset of forward systolic flow was significantly longer in patients with aortic stenosis than in the control population (185 (8.5) v 85 (10) ms, p < 0.01). The time from the onset of diastolic flow to peak diastolic velocity was also significantly longer in the aortic stenosis group (146 (16) v 74 (13) ms, p < 0.01). These abnormalities in profiles of coronary flow were reversed by replacement of the aortic valve. There was no correlation between changes in flow profiles in patients with aortic stenosis and preoperative clinical history, transvalvar gradient, left ventricular mass index, or ventricular dimensions.

CONCLUSIONS

Coronary flow profiles in patients with aortic stenosis were characterised by reversed early systolic flow and delayed forward systolic flow and attainment of peak diastolic velocity. Reversal of these abnormalities by replacement of the aortic valve may reflect altered left ventricular and aortic haemodynamics and contribute to the relief of angina when left ventricular hypertrophy persists. Further studies may correlate abnormalities of coronary flow with preoperative clinical and haemodynamic state.

Conservative surgery of the mitral valve: a report of the first 100 cases from one unit and one surgeon

OBJECTIVE

To report the first 100 mitral valve repairs performed in a unit with an aggressive approach to conservative mitral valve surgery.

DESIGN

Case notes were reviewed retrospectively and patients invited for clinical examination and cross sectional and Doppler echocardiography.

SETTING

Tertiary cardiothoracic referral centre.

PATIENTS

Between December 1985 and April 1991 mitral valve repair was carried out on 100 patients (66 males). Patients with pure mitral stenosis were excluded. Sixty seven had degenerative and 15 rheumatic mitral valve disease. Median age was 66 (range 12 to 79) years, with an interquartile range of 59 to 71 years.

INTERVENTIONS

Operative procedures included annuloplasty ring in 97, resection of the posterior leaflet in 67, resection of endocarditic portion of posterior leaflet in four, commissurotomy in six, and correction of anterior leaflet abnormalities in seven. Thirty nine concomitant cardiac procedures were performed in 32 patients. Six operations were emergencies, and three of these required concomitant procedures.

MAIN OUTCOME MEASURES

Mortality, operative failure rate, patients' functional state and degree of residual mitral regurgitation, incidence of thromboembolism, and endocarditis.

RESULTS

Follow up ranged from one to 59 months, median 14 months, and an interquartile range of four to 23.5 months. Early mortality was 1%, late mortality 5%, and there was a 2% reoperation rate. Eighty four patients had moderate to severe mitral regurgitation preoperatively. At follow up mitral regurgitation was absent or mild in 78. Eighty six patients were in New York Heart Association (NYHA) class I-II at follow up compared with 80 in NYHA class III-IV preoperatively. There were no thromboembolic events.

CONCLUSION

This study shows that satisfactory results can be obtained with mitral valve repair in a fairly elderly population with a high incidence of concomitant cardiac disorders. We suggest that these encouraging results will lead to earlier mitral valve repair in mitral regurgitation.

Hemodynamic evaluation of the Monostrut and spherical disc Björk-Shiley aortic valve prosthesis with Doppler echocardiography

A Doppler echocardiographic study was performed to assess whether the Monostrut model of the Björk-Shiley valve (Shiley, Inc., Irvine, Calif.) had an improved hemodynamic performance in comparison with the spherical disc model in the aortic position. Twenty retrospectively randomly selected patients were studied, 10 with each valve type. Within each valve type two sizes of valve were studied, 21 and 23 mm. The two groups were comparable with respect to age, postoperative time, fractional shortening, New York Heart Association functional class preoperatively, and body surface area. Pulsed and continuous wave Doppler measurements were recorded at rest. Continuous wave Doppler recordings were performed every 2 minutes after exercise with supine bicycle ergometry until 10 minutes after exercise. Peak and mean gradients across the aortic valve prostheses were estimated. Both groups achieved a significant and comparable rise in heart rate with exercise. The mean gradients +/- standard error of the mean at rest and 2 minutes after exercise were 19.7 +/- 1.9 mm Hg and 30.9 +/- 2.2 mm Hg, respectively in the spherical disc group compared with 14.9 +/- 1.1 mm Hg and 23.6 +/- 1.7 mm Hg in the Monostrut group (p < 0.05 and p < 0.025, respectively). Peak transvalvular gradient at rest was 30.7 +/- 2.7 mm Hg in the spherical group compared with 23.9 +/- 1.9 mm Hg in the Monostrut group (p < 0.05). We conclude that the Monostrut Björk-Shiley valve prosthesis has better hemodynamic performance than the spherical disc model in the aortic position.

Sudden cardiac death in athletes

Sudden death in athletes is a rare but tragic occurrence. Congenital cardiovascular abnormalities, usually asymptomatic and often undiagnosed during life, are the main causes in young athletes. Hypertrophic cardiomyopathy and congenital coronary anomalies are the most commonly occurring disorders. Idiopathic concentric left ventricular hypertrophy (non-physiological), arrhythmogenic right ventricular dysplasia and Marfan's syndrome with aortic rupture have also been implicated. Rarer causes include mitral valve prolapse and myocarditis. Coronary atherosclerosis is the major cause in older, and occasionally in younger athletes. Those involved in the medical care of athletes should be aware of the potential causes of sudden death in these groups. Symptomatic athletes should be fully investigated. Screening programmes are probably not justified on a cost effective basis.

Transthoracic high-frequency two-dimensional echocardiography, Doppler and color flow mapping to determine anatomy and blood flow patterns in the distal left anterior descending coronary artery

Combined high-frequency transthoracic ultrasound, pulsed Doppler and color flow mapping were used to image and assess blood flow velocity in the distal left anterior descending artery (LAD) in 56 consecutive patients. All patients subsequently underwent coronary angiography. The LAD was imaged in 19 patients (34%), and the diameter was measured in 12 with high-quality images (mean diameter 1.8 mm +/- 0.08). In 1 patient, the penetrating branches of the LAD were imaged. The distal LAD appeared normal by ultrasound in 18 patients, and a significant stenosis was detected in 1; angiography confirmed the ultrasound findings. There were no false negative results. Characteristic biphasic flow with higher velocities in diastole were noted in all 19 patients. Color flow mapping demonstrated normal laminar flow, except in the patient with a distal stenosis. Pulsed Doppler confirmed an increased velocity distal to the stenosis in this patient. This study is the first transthoracic evaluation of the hemodynamic effects of a coronary artery stenosis, and the first in vivo description of blood flow disturbance at a distal coronary stenosis in humans. The clinical use of this technique is limited, because only the distal portion of the LAD is visualized. However, it may provide a noninvasive means of assessing distal LAD diameter and blood flow, and changes in these parameters under a variety of physiologic, pharmacologic and interventional stimuli.

Morphologic consequences of systematic training

The development of echocardiography in the 1970s led to the flourishing of the study of the athlete's heart. From the earliest studies it was apparent that athletes develop enlargement of the left ventricular cavity and thickening of myocardium in response to prolonged repetitive training. The changes in echocardiographic measurements are small and often within quoted normal ranges. By comparison to sedentary controls, however, left ventricular end-diastolic dimension is increased by approximately 10%, posterior wall dimension by 15% to 20%, and calculated mass by up to 45%.

Experience of percutaneous transluminal coronary angioplasty in orthotopic cardiac transplant recipients

We evaluated the role of percutaneous transluminal coronary angioplasty (PTCA) in a series of orthotopic cardiac transplant recipients with severe epicardial coronary occlusive disease. Ten orthotopic cardiac transplant patients treated by PTCA up to March 1990 were reviewed. All had significant epicardial coronary artery lesions (greater than 70% stenosis compared with the adjacent healthy artery) and exercise electrocardiogram or isotope perfusion evidence of myocardial ischaemia in the relevant region. Primary angiographic PTCA success was achieved in 12 of the 16 lesions attempted (75%). Mean stenosis improvement was from 80% of adjacent healthy artery (range 70-90%) to 12% (range 0-20%). Median angiographic follow-up of 9 months (2-25 months) is available for all patients. The mean recurrence rate is 33% (4 of 12 successfully treated lesions) defined as greater than 50% reduction in the original gain at the PTCA. We have shown that PTCA is technically possible in a series of cardiac transplant recipients. The primary success and recurrence rates are comparable to the use of PTCA in conventional atherosclerotic coronary disease.

Ambulatory electrocardiography in dogs

Twenty-four hour ambulatory electrocardiographic recording using a Medilog tape recorder was attempted in 16 healthy pet dogs weighing between 18.4 and 34 kg, while they were living in familiar surroundings. Full 24-hour records were obtained from 10 of them and recordings of more than 10 hours duration from two others; and the findings in these recordings were similar. Maximum heart rates ranged between 110 and 300 beats/minute and the minimum rates ranged between 17 and 46 beats/minute. Intermittent ventricular premature complexes were recorded from these apparently healthy dogs and all but one dog demonstrated a sinus pause, longer than two seconds; the longest pause was 5.7 seconds. The pauses were associated with marked sinus arrhythmia and occurred in both brachycephalic and non-brachycephalic breeds.

Histopathological validation of high frequency epicardial echocardiography of the coronary arteries in vitro

The accuracy and reliability of measurement of coronary artery dimensions and detection of atherosclerotic lesions by high frequency epicardial echocardiography were compared with histopathological results. Ten pressure perfused human hearts were examined in vitro with a 10 MHz (Diasonics) transducer and a 7.5 MHz (Vingmed/Sonotron) transducer. There was close agreement between ultrasound and pathological measurements of coronary artery luminal diameter. Qualitative changes in wall structure such as diffuse wall thickening and calcification were readily identified; however, the resolution of the transducers was not high enough accurately to measure wall dimensions in normal coronary arteries. Coefficient of variation measurements for intra and inter observer variability (5.2% and 6.9% respectively) showed excellent reproducibility. The technique was accurate in identifying atherosclerotic lesions, imaging arteries distal to an occlusion, locating deeply sited arteries, and identifying complete obliteration of an artery. Intraoperative video playback and transducer miniaturisation may minimise problems caused by cardiac movement and restricted access. With these developments intraoperative assessment of coronary artery disease may become a real possibility.

Pituitary apoplexy following coronary artery bypass surgery

Pituitary apoplexy is a syndrome with variable clinical manifestations depending on which parasellar structures (such as the optic nerves and chiasm, cavernous and sphenoid sinuses, or the hypothalamus) are compressed when the pituitary undergoes rapid enlargement. Factors associated with cardiopulmonary bypass that may lead to pituitary apoplexy include ischemia, hemorrhage, edema, and positive pressure ventilation. Seven cases of pituitary apoplexy following cardiopulmonary bypass have been reported, including the present case. Transsphenoidal surgical decompression in the present case and those previously reported appears to be safe after cardiac surgery and may be helpful in amelioration of compression of nearby structures. Pituitary apoplexy should be considered as a diagnostic possibility in patients who develop visual disturbances or ophthalmoplegia following open heart surgery.