Intraoperative Cardiac Monitoring Research Articles

Transesophageal Echocardiographic Evaluation of a Double Orifice Mitral Valve

Intraoperative transesophageal echocardiography currently is used routinely for many cardiothoracic surgical procedures. Although it is often used for intraoperative cardiac monitoring and to confirm preoperative echocardiographic findings, it may sometimes result in the discovery of unexpected pathology. In this e-challenge, a patient was found to have a mitral valve abnormality that was not previously detected on the preoperative transthoracic echocardiogram. The mitral valve anomaly subsequently was evaluated to characterize the anatomy, interrogate the valve, and provide a diagnosis.

Severe Pulmonary Hypertension and Right Ventricular Failure Complicate a Total Abdominal Hysterectomy

The 2007 American College of Cardiology/American Heart Association guidelines report that no significant studies have been conducted assessing the perioperative risk of pulmonary hypertension in noncardiac surgery. However, the presence of right ventricular failure has been well documented to have poor prognostic implications. The presence of pulmonary hypertension and right ventricular failure present unique perioperative challenges. These include maintenance of adequate cardiac function, acid-base management, intraoperative monitoring, and postoperative pain management. The authors report the case of a patient with severe pulmonary hypertension who underwent an open total abdominal hysterectomy. The case was complicated by known right ventricular failure, severe portal hypertension, obstructive sleep apnea, extensive smoking history, and systemic anticoagulation therapy. The patient was not a candidate for postoperative neuraxial analgesia because of the timing and dose of systemic anticoagulation. Two-dimensional transesophageal echocardiography was used for real-time visualization and intraoperative cardiac monitoring. The patient was transferred to the intensive care unit for careful titration of opioids and slow ventilator wean to extubation. The postoperative course proceeded without significant morbidity or mortality. (a) Preoperative assessment of pulmonary hypertension, (b) postoperative pain control, (c) cardiovascular stability, and (d) intraoperative monitoring. This case illustrates the unique challenges associated with pulmonary hypertension and right ventricular failure in the setting of noncardiac surgery. This case also demonstrates that continuous, real-time data provided by transesophageal echocardiography can be used to successfully manage a complicated patient with pulmonary hypertension.

Dynamic real-time 4D cardiac MDCT image display using GPU-accelerated volume rendering

Intraoperative cardiac monitoring, accurate preoperative diagnosis, and surgical planning are important components of minimally-invasive cardiac therapy. Retrospective, electrocardiographically (ECG) gated, multidetector computed tomographical (MDCT), four-dimensional (3D + time), real-time, cardiac image visualization is an important tool for the surgeon in such procedure, particularly if the dynamic volumetric image can be registered to, and fused with the actual patient anatomy. The addition of stereoscopic imaging provides a more intuitive environment by adding binocular vision and depth cues to structures within the beating heart. In this paper, we describe the design and implementation of a comprehensive stereoscopic 4D cardiac image visualization and manipulation platform, based on the opacity density radiation model, which exploits the power of modern graphics processing units (GPUs) in the rendering pipeline. In addition, we present a new algorithm to synchronize the phases of the dynamic heart to clinical ECG signals, and to calculate and compensate for latencies in the visualization pipeline. A dynamic multiresolution display is implemented to enable the interactive selection and emphasis of volume of interest (VOI) within the entire contextual cardiac volume and to enhance performance, and a novel color and opacity adjustment algorithm is designed to increase the uniformity of the rendered multiresolution image of heart. Our system provides a visualization environment superior to noninteractive software-based implementations, but with a rendering speed that is comparable to traditional, but inferior quality, volume rendering approaches based on texture mapping. This retrospective ECG-gated dynamic cardiac display system can provide real-time feedback regarding the suspected pathology, function, and structural defects, as well as anatomical information such as chamber volume and morphology.

Perioperative Surveillance for Adverse Myocardial Events

Perioperative myocardial infarctions occur in 1 to 4% of unselected noncardiac surgical patients, and are associated with high mortality. Detection of these events can be challenging, because 'typical' symptoms of myocardial ischemia may not be present or may be masked in the perioperative period. Therefore, surveillance by means of intraoperative cardiac monitoring and postoperative serial electrocardiograms (ECGs) and troponins may be needed. Cardiac monitoring not infrequently detects ST-segment changes suggestive of ischemia during or shortly after surgery. To respond to these changes, the risk for coronary artery disease should be assessed before recommending additional interventions. For all vascular surgery patients, and for patients who have or are felt to be at risk for coronary artery disease, serial postoperative 12-lead ECGs and troponins should be considered. Among surgical patients not meeting these criteria, obtaining routine ECGs in the absence of signs or symptoms that suggest a cardiac event may be falsely reassuring and is not felt to be useful. The presence of elevated postoperative troponins predicts worsened prognosis, and argues for intensified risk factor modification. The need for noninvasive cardiac testing or cardiac catheterization should be made on an individual basis.

Sacral nerve neuromodulation in patients with cardiac pacemakers

The objective of the study was to describe our experience using sacral nerve neuromodulation for urinary urgency, frequency, and urge incontinence in patients with cardiac pacemakers. The study was a case series of 3 patients with cardiac pacemakers who underwent sacral nerve stimulation for refractory urgency, frequency, and urge incontinence. Each patient underwent placement of an InterStim lead wire in the S3 foramen. Intraoperative cardiac monitoring revealed no evidence of cross-interference, even at maximum stimulation. Postoperative telemetry for 24 hours did not reveal any interference from the sacral nerve stimulator. All patients had a greater than 50% reduction in incontinence episodes during their test trial and underwent placement of the InterStim implantable pulse generator (IPG). Intraoperative and postoperative IPG programming was done with cardiac monitoring; no interaction was detectable. Sacral nerve stimulation appears to be safe in the presence of a cardiac pacemaker.

Strabismus Surgery Under Augmented Topical Anesthesia

Recently, topical lidocaine 2% jelly had been used in phacoemulsification and trabeculectomy surgeries. The purpose of this study is to evaluate the efficacy and stability of one-stage adjustable suture using topical lidocaine jelly 2% in combination with intravenous nalbuphine (Nubain). Forty adult patients aged 16 to 46 years (median, 24 years) underwent adjustable rectus muscle surgery under topical lidocaine jelly 2% and intravenous 10 mg nalbuphine given 10 minutes before surgery. Adjustment was performed on the operating table before conjunctival closure. The stability of adjustment was studied by comparing the postadjustment deviation to that at 1 day, 1 week, and 3 weeks postoperatively. Success was defined as alignment within 10 prism diopters on distant fixation. Analgesia was assessed using Verbal Description Scale. Changes in vital signs were recorded during surgery to evaluate the oculocardiac reflex. Forty rectus muscles were recessed, 22 muscles were resected, 3 muscles were tucked, and 2 muscles were retrieved. During the operation, 35 patients expressed no pain, 3 patients complained of discomfort, and 2 patients complained of distressing pain and required an additional 10 mg of intravenous nalbuphine. Thirty-eight patients (95%) were successfully aligned during the first postoperative day, 37 patients (92.5%) after 1 week, and 36 patients (90%) after 3 weeks. Intraoperative cardiac monitoring did not record positive oculocardiac reflex in any patient. Lidocaine jelly in combination with intravenous nalbuphine is an effective topical anesthesia strategy that provides for the patient's comfort and the surgeon's ability to fine-tune ocular alignment on the operating table.

Automated Echocardiographic Analysis

Although transesophageal echocardiography allows continuous intraoperative cardiac monitoring, the technique has been limited by the lack of a method for realtime, quantitative assessment of cardiac chamber size and systolic function. Automated border detection (ABD), based on an analysis of integrated backscatter, is a new technique that is purported to provide real-time, quantitative assessment of left ventricular (LV) areas and fractional area change (FAC). A prospective investigation was designed to assess the accuracy and trending capability of ABD during continuous intraoperative monitoring. In 16 patients monitored throughout noncardiac surgical procedures, serial real-time estimates of LV end-diastolic area (EDA), end-systolic area (ESA), and FAC by ABD were compared with paired off-line manual measurements made by two experiences echocardiographers. There was a high correlation between real-time ABD estimates of LV ESA (r = 0.93), EDA (r = 0.89), and FAC (r = 0.90) to those of the off-line technique. The automated technique systematically underestimated both EDA and ESA, resulting in a small underestimation of FAC. The automated technique demonstrated an accuracy rate of 96% in tracking serial changes in LV area. The technique performed with an 83% sensitivity and 85% specificity for detecting acute changes in LV area. This analysis of serial intraoperative echocardiograms demonstrates the accuracy of ABD to estimate LV area in real time and to track serial changes in cardiac area during surgery. Although ABD is an automated technique, application by personnel experienced in its operation and an echocardiographic system that includes lateral-gain adjustment controls are recommended for its optimal performance.

Intraoperative cardiac output monitoring: Comparison of impedance cardiography and thermodilution

Impedance cardiography (IC) is a noninvasive, simple to use method of cardiac output (CO) determination. A prospective evaluation of IC monitoring was performed in 50 patients undergoing noncardiac surgery. IC CO measurements (NCCOM3-Revision 7, BoMed Manufacturing) were compared to simultaneous measurements of thermodilution (TD) CO to assess the validity of this technique for intraoperative cardiac monitoring. Adequate impedance signals could not be obtained in 7 of the 50 patients. IC CO measurements were highly correlated to TD CO ( P < .005), with a correlation coefficient r = 0.84. Bias analysis, however, indicated clinically significant disagreement between the two techniques. IC CO tended to underestimate TD CO (mean bias = -0.41 L/min) and the SD of the bias was 1.0 L/min (95% level of agreement 1.6 to -2.4 L/min). Trending data showed IC to accurately track the direction of TD CO changes but to underestimate their magnitude (r = 0.60, intercept -0.7 L/min, slope 0.47). Factors that may have impaired the performance of IC in this study include the high prevalence of cardiac disease in the study population and electrical noise in the operative setting. Further development of IC appears warranted if it is to prove useful as an intraoperative cardiac monitor.

A clinical computer database entry form for an intraoperative anesthesiology-based transesophageal echocardiography monitoring service.

Transesophageal echocardiography (TEE) has been increasingly applied to supplement and, in instances, to supplant conventional intraoperative cardiac monitoring. Our body of experience (> 1600 intraoperative TEE procedures), combined with insights gleaned from an intramural quality assurance study, and clinical implications of certain recent advances in the field, led us to develop the following TEE computer database entry form. The form, completed intraoperatively, consists of a patient and surgical procedure demographics section, followed by fields based on the TEE examination. The scans encompass transverse plane basal short axis, long axis, and transgastric views of the heart and great vessels. The two-dimensional echocardiographic, saline-contrast, color flow and pulsed Doppler data represent both right and left ventricular performance, valvular function and specific lesions. This database entry form is intended to serve as a guide for performance of a nominally complete intraoperative study and facilitate maintenance of a TEE archive consistent with current advances.