Cardiovascular Anesthesiology: Echo Rounds
A 52-yr-old man with severe occlusions in his proximal left anterior descending (LAD) and left circumflex arteries underwent off-pump coronary artery bypass (OPCAB) surgery under transesophageal echocardiographic (TEE) monitoring. After completing the left internal mammary artery–LAD anastomosis, the surgeon attempted marked cardiac displacement (“verticalization”) to perform the distal anastomosis of the radial arterial graft to the obtuse marginal branch using an apical positioner (Urchin™, Medtronic, Minneapolis, MN) and lap pads. Intractable hemodynamic compromise developed at every attempt and was refractory to our efforts to optimize the intravascular volume and perfusion pressure, despite using the Trendelenburg position, adjusting the degree of displacement, and administering fluid or a vasoconstrictor with a low-dose inotrope. During the attempt, the amplitude of 2-lead electrocardiographic signal to detect ST changes was markedly reduced, and the midesophageal (ME) TEE imaging was insufficient for helping the surgeon to find the optimal degree of displacement and stabilization because of the reduced image quality. In particular, the transgastric (TG) TEE imaging of the mid-to-apical inferolateral left ventricular (LV) wall was completely obscured by the echogenic shadow of the lap pads (Fig. 1A). (See Supplemental Digital Content 1, Video1, http://links.lww.com/AA/A9 [the transgastric long-axis view shows that the imaging of the mid-to-apical inferolateral left ventricular wall was compromised because of the echogenic shadow of the lap pads underneath the displaced heart (this image was from another case for comparison)]).
After restoring stable hemodynamics by releasing the displacement, we decided to place a bag consisting of a surgical glove filled with 200 mL of normal saline, instead of lap pads, underneath the heart to facilitate TG TEE imaging during cardiac displacement. Through several trials involving fine adjustment of the displacement to avoid dyskinesia in the midventricular inferolateral LV wall in the enhanced TG images (Figs. 1B and C) (Supplemental Digital Content 2, Video 2, http://links.lww.com/AA/A10 [The transgastric (TG) long-axis view and the midventricular TG short-axis view after placing the saline bag underneath the displaced heart show dyskinesia in the midventricular inferolateral and the inferolateral left ventricular wall; the anteroseptal wall shows hypokinesia and reduced thickness; the dyskinetic inferolateral wall shows no systolic wall thinning.]), the position of the heart and apical stabilizer allowing the maximal surgical access and least compromise in LV wall motion was achieved (Fig. 1D) (Supplemental Digital Content 3, Video 3, http://links.lww.com/AA/A11 [The midventricular transgastric short-axis view with the saline bag shows no compromise in left ventricular wall motion during graft construction for the distal obtuse marginal branch.]). A suction-type tissue stabilizer (Octopus™, Medtronic) was then applied to the target area of the obtuse marginal branch to construct the anastomosis, and an intracoronary shunt was used to avoid further compromise during graft construction. Simultaneously, the velocity-time integral of the aortic valvular flow measured using continuous wave Doppler in the enhanced TG long-axis view was monitored frequently as a surrogate marker of the cardiac output (CO)1 during graft construction (Fig. 2). The graft patency and improvement in regional wall motion (RWM) were assessed immediately after graft construction, and the patient was transferred to the intensive care unit.
Our case demonstrates how the use of a saline bag facilitated TG TEE imaging and enhanced the clinical efficacy of transesophageal echocardiography during cardiac displacement in OPCAB surgery. TEE monitoring focusing on deteriorating ventricular function, RWM, and valvular function prompts rapid interventions in OPCAB surgery because the deterioration noted on TEE imaging usually precedes cardiovascular collapse. However, TEE imaging during graft construction is usually limited to the ME view because the cardiac displacement and lap pads interfere with transmission of the ultrasonic signal and compromise the TG views. The ME views obtained by directing the imaging plane through the left atrium toward the LV are thought to allow comprehensive monitoring of RWM during cardiac displacement.2 Even with this, however, some LV segments can be obscured because of deviation of the LV wall beyond the imaging plane, with severe cardiac retraction and echocardiographic shadows resulting from proximal calcified structures in the aortic and mitral valves in some patients. Furthermore, more vigorous cardiac lifting and tilting is required for sufficient surgical assessment of the distal anastomosis of the left circumflex artery graft than with LAD anastomosis, which is often associated with poorer quality TEE imaging, whereas much closer monitoring for early detection and management may be required when more pronounced hemodynamic compromise occurs.
Because the sensitivity of the electrocardiographic changes is probably reduced and its polarity is altered during cardiac displacement,3 the enhanced TG short-axis view that results from placing the saline bag makes it easier to monitor RWM and myocardial ischemia specific to each coronary artery territory. However, newly developed RWM abnormalities, which are detected by transesophageal echocardiography at the reduction of preload during cardiac displacement and stabilization, do not always mean myocardial ischemia.4
Determining the real-time CO using aortic velocity-time integral monitoring1 through the enhanced TG view during graft construction is an additional benefit, considering that beat-to-beat maintenance of an adequate CO is important and the CO derived from the thermodilution pulmonary artery catheter is sometimes distorted by the limited right ventricular wall motion and aggravated tricuspid regurgitation that occurs during this period.5 Unlike lap pads, the shape of the saline bag accommodates the systolic-diastolic motion of the LV wall well. It may be a potential benefit for relieving ventricular compression and possible hemodynamic compromise during marked cardiac displacement.
1.Grow MP, Singh A, Fleming NW, Young N, Watnik M. Cardiac output monitoring during off-pump coronary artery bypass grafting. J Cardiothorac Vasc Anesth 2004;18:43–6
2.Wang J, Filipovic M, Rudzitis A, Michaux I, Skarvan K, Buser P, Todorov A, Bernet F, Seeberger MD. Transesophageal echocardiography for monitoring segmental wall motion during off-pump coronary artery bypass surgery. Anesth Analg 2004;99:965–73
3.Shanewise JS, Ramsay JG. Off-pump coronary surgery: how do the anesthetic considerations differ? Anesthesiol Clin North America 2003;21:613–23
4.Seeberger MD, Cahalan MK, Rouine-Rapp K, Foster E, Ionescu P, Balea M, Merrick S, Schiller NB. Acute hypovolemia may cause segmental wall motion abnormalities in the absence of myocardial ischemia. Anesth Analg 1997;85:1252–7
5.Do QB, Goyer C, Chavanon O, Couture P, Denault A, Cartier R. Hemodynamic changes during off-pump CABG surgery. Eur J Cardiothorac Surg 2002;21:385–90
By Drs. Nikolaos Skubas, Roman Sniecinski, and Martin J. London
OPCAB surgery requires significant displacement of the heart away from the esophagus, making TEE imaging challenging.
In this case, the authors were able to improve TEE imaging of the myocardium by using a saline-filled glove instead of the commonly used lap pads or deep pericardial stay sutures behind the heart.
In addition to 2-dimensional imaging of the LV for monitoring of wall motion abnormalities, the systolic velocity in the LV outflow tract recorded with pulsed wave Doppler can be used to monitor LV stroke volume during LV displacement.