Mark J. Callahan

Doppler Echocardiography: Theory, Instrumentation, Technique, and Application

A Doppler examination is a valuable adjunct to a complete echocardiographic examination. It has the capability of measuring normal and abnormal velocities of blood flow noninvasively. For the first time, this procedure allows noninvasive quantitation of stenotic gradients, intracardiac pressures, and blood flow as well as semiquantitative assessment of regurgitant lesions. With this procedure, the operator must progress through a learning curve in order to gain a complete understanding of the examination techniques, the limitations of the instruments, and the Doppler physics principles before applications can be made to clinical practice. Evaluation of other aspects of Doppler echocardiography, such as color-flow mapping and assessment of diastolic events, portends great promise for the role of this procedure in the future.

Noninvasive Measurement of Cardiac Output by Continuous-Wave Doppler Echocardiography: Initial Experience and Review of the Literature

Doppler echocardiographic measurement of the velocity of blood flow in the ascending aorta is a noninvasive method for determining cardiac output in the critically ill patient. Fifty-four patients in the medical intensive care unit (35 men and 19 women, age range 41 to 91 years) in whom a Swan-Ganz catheter had been inserted underwent measurement of cardiac output with use of a commercially available continuous-wave Doppler echocardiographic instrument. The aortic root diameter was measured by A-mode echocardiography. An additional 26 patients (17 men and 9 women, age range 20 to 83 years) who had undergone an open-heart surgical procedure and had hemodynamic monitoring in the postoperative period also underwent Doppler measurement of cardiac output. In these patients, the aortic root diameter was measured directly intraoperatively. Cardiac output was also determined by thermodilution in both groups. An adequate A-mode study was possible in 83% of the medical patients but only 27% of the surgical patients. Doppler signals were adequate in 84% of the medical patients and 92% of the surgical patients. The correlation between thermodilution and Doppler-derived cardiac output was good in both the medical (r = 0.94, SEE = 0.78, P less than 0.001) and the surgical (r = 0.85, SEE = 0.78, P less than 0.001) group. Doppler echocardiography is a promising noninvasive method for determining cardiac output in critically ill patients.

Evaluation of intraoperative transesophageal two-dimensional echocardiography

Transesophageal two-dimensional echocardiography (TEE) was evaluated in 11 patients who underwent myocardial revascularization. The TEE transducer was positioned to view the left ventricular (LV) short-axis at the level of the papillary muscles (midcavity). Good quality echocardiographic images were obtainable in ten of 11 patients. Global LV function was assessed by measuring LV end-diastolic and end-systolic area and computing the fractional area change (FAC). Measurements of LV areas and FAC had excellent intraobserver reproducibility. Regional LV function was analyzed in two ways after dividing the short-axis view of the LV into four or five anatomic segments. Systolic wall thickening (SWT) of the myocardium was measured in each of four segments by digitization of the endocardial and epicardial borders of the LV and determining the fractional wall thickening. Measurements of SWT were not reproducible, primarily because of a difficulty in delineating the epicardial border of the LV accurately. In the second method, regional wall motion (RWM) in each of five segments was graded according to a previously developed scoring system. RWM analysis proved to be a measurement with excellent interobserver and intraobserver reproducibility. TEE was performed without complication and found to be a reproducible method for assessing global and regional LV function. Quantitative analysis is tedious and, therefore, currently not available on-line in the operating room.

Validation of instantaneous pressure gradients measured by continuous-wave Doppler in experimentally induced aortic stenosis

The relation between catheter-measured and Doppler-derived aortic pressure gradients was examined in 8 open-chest dogs. A snare was placed around the proximal ascending aorta and adjusted to provide a wide range of gradient to left ventricular (LV) outflow. A continuous-wave Doppler transducer was placed above the level of the obstruction and angled to optimize the audio and spectral signals. Pressure tip transducer catheters recorded LV and ascending aortic pressures simultaneously with the Doppler signal. In 120 randomly selected sinus beats, Doppler-derived maximal gradient correlated well with maximal instantaneous catheter gradient from 4 to 179 mm Hg (r = 0.99). Mean gradients also were closely related (r = 0.98). For gradients above 100 mm Hg, the correlation remained good (r = 0.98), but for gradients below 50 mm Hg, the correlation was not as precise (r = 0.81). All 120 cycles were digitized at 10-ms intervals to examine the correspondence between the Doppler and catheter data throughout systole. For the 2,742 pairs of points so obtained, the correlation was excellent (r = 0.95). The close relation between Doppler-derived pressure gradient and that measured simultaneously by catheterization provides further validation of the use of continuous-wave Doppler in the assessment of aortic stenosis, not only at maximal gradient, but throughout the period of LV ejection.

Position-Dependent Ventricular Tachycardia Related to a Peripherally Inserted Central Catheter

Recently, peripherally inserted central venous catheters (PICCs) have been widely used for venous access. Advantages of a PICC over centrally inserted central catheters include the virtual elimination of the risk of pneumothorax, hemothorax, and arterial puncture, along with a reduced risk of bleeding. However, the PICC has associated risks. We present 2 cases of body position-dependent ventricular tachycardia related to PICCs. These events occurred in patients with no prior history of cardiac arrhythmia and were corrected by repositioning of the PICC. They serve to identify a potentially serious cardiac complication of the PICC that, to our knowledge, has not been described previously.

Transient atrioventricular block after open-heart surgery for congenital heart disease.

The records of 22 patients with transient atrioventricular (AV) block after open-heart surgery for congenital heart disease from 1972 to 1978 were reviewed to determine the natural history of this entity. Preoperatively, no patient had AV block; 3 had right bundle branch block (BBB), 1 had left BBB and 5 had nonspecific intraventricular conduction delay. Complete AV block developed in 20 patients and Mobitz II AV block in 2. Transient AV block occurred intraoperatively in 14 patients and within 48 hours postoperatively in 8; AV block persisted for greater than or equal to 48 hours postoperatively in all patients, for a mean of 7.3 days (range 2 to 28). During a follow-up of 5.5 years (range 2.5 to 10), late AV block developed in 2 patients. None of the 18 patients whose escape QRS complex morphology during AV block was similar to the final QRS complex during normal sinus rhythm or atrial fibrillation with AV conduction had late AV block, whereas 2 of the 4 in whom it differed did (p less than 0.01). There was no difference in the escape rate between the 2 groups. Thus, late development of high-grade AV block is infrequent among patients with transient postoperative AV block. An escape QRS complex during postoperative AV block that differs from the QRS complex seen on recovery of normal sinus rhythm or atrial fibrillation with anterograde conduction may identify those at high risk of late AV block.

Myocardial stunning in hypertrophic cardiomyopathy: Recovery predicted by single photon emission computed tomographic thallium-201 scintigraphy

A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.

Acquired right atrial blood cyst: a hitherto unrecognized complication of cardiac operation

Blood-filled cysts within the heart are rare anomalies, usually congenital, and are seen predominately in infants. We report an unusual case of a 68-year-old woman with an acquired right atrial blood-filled cyst that developed after mitral and tricuspid valve operation and that was detected using 2-dimensional echocardiography. We propose that surgical trauma resulted in the formation of the cyst.

Paraneoplastic Digital Thrombosis: A Case Report

Persistent digital ischemia is an uncommon paraneoplastic syndrome. We describe a 71-year-old man whose only manifestation of an underlying adeno carcinoma was digital ischemia. His symptoms responded dramatically to bilat eral dorsal sympathectomies. A thorough search for the mechanism producing the ischemia failed to provide an explanation. We assume that unknown neuro- humoral factors produced by the tumor were responsible.

Severe Left Atrial Appendage Stunning After Electrical Cardioversion of Atrial Fibrillation

A 77-year-old man with a history of ischemic cardiomyopathy presented with 3 days of progressively worsening dyspnea. An ECG revealed atrial fibrillation at a rate of 97 bpm. An echocardiogram showed severe left atrial enlargement, severely elevated left ventricular filling pressure, and an ejection fraction of 30%. Thyroid function …