We completely agree with Michaux et al.1 that more studies are needed to establish normal values of right ventricular function in anesthetized patients. More importantly, however, interpretation of normal values will depend heavily upon echocardiographic techniques involved in acquiring these data. Ultimately, future studies will be important in establishing abnormal thresholds of right ventricular function associated with poor postoperative outcomes.
The right ventricle and right atrium have been shown to dilate slightly (approximately 10%) after induction of anesthesia and mechanical ventilation.2–4 Flow velocities such as tricuspid inflow usually decrease after induction of anesthesia.2–4 Right ventricular fractional change and tricuspid annular plane usually decrease by approximately 5%-10%. Normal values of right ventricular (RV) myocardial performance index have not been well described in the literature. In a small series published by our group (n = 16), RV myocardial performance index was measured at 0.32 ± 0.09 in patients with normal pulmonary pressures and without valvular or right coronary artery disease.5
The question of tricuspid annular velocities (TAV) is more complex. TAV is often used as a surrogate of regional ventricular work and depends on both the loading conditions and RV contractility. Unfortunately, in the literature, a lack of standardized technique has resulted in confusion about the effect of anesthesia on these values. First of all, pulsed wave Doppler techniques are not equivalent to those derived from color Doppler. Pulsed wave tissue Doppler measures the peak velocity, whereas color tissue Doppler measures the “average” velocity over the sample area in question. The size of the sample area is unfortunately infrequently stated in the literature, and there is no accepted standard size. We have used 6 × 6 mm as our standard. TAV using both these methods yields different results. For example, Tumuklu et al.6 found in a normal group a TAV of 16 ± 2 cm/s using pulsed-wave tissue Doppler imaging and 10.8 ± 1.6 cm/s using color tissue Doppler. Sample location is also very important. The lateral wall of the RV is amenable to tissue Doppler interrogation using transthoracic echocardiography (TTE). It is not, however, using transesophageal echocardiography (TEE). A transgastric approach must be used.7 Using color tissue Doppler, it has been found that the values at the lateral wall using TTE are not equivalent to those in the inferior wall using a transgastric TEE approach: 8.98 ± 1.96 vs 5.88 ± 1.83 cm/s, respectively. Only the isovolumic acceleration appeared to be equivalent.8 The transgastric systolic velocity values were slightly lower in a study by David et al.7 (4.34 ± 1.19) possibly owing to differences in cardiac disease or loading conditions. They were significantly reduced after bypass. Therefore, preoperative TTE data cannot be compared with postinduction TEE data.
Preinduction TEE examinations are generally not possible. We have recently studied the impact of induction of anesthesia and ventilation using TTE and color tissue Doppler in cardiac patients and normal volunteers (in review). We found a significant decline in tricuspid annular plane systolic excursion postinduction, however, no changes in isovolumic acceleration or systolic velocities. If further validated, these parameters may prove to be useful in stratifying patients undergoing cardiac surgery (Table 1).
François Haddad, MD
Claude P. Tousignant, MD
Pierre Couture, MD
André Denault, MD
Department of Anesthesiology
Montreal Heart Institute and Université de Montréal
Montreal, Quebec, Canada
1. Michaux I, Filipovic M, Seeberger M, Skarvan K. Are normal echocardiographic values obtained by transthoracic echocardiography in awake patients suitable for evaluation of cardiac function in anesthetized and mechanically ventilated patients? Anesth Analg 2009;109:1701
2. Couture P, Denault AY, Shi Y, Deschamps A, Cossette M, Pellerin M, Tardif JC. Effects of anesthetic induction in patients with diastolic dysfunction. Can J Anaesth 2009;56:357–65
3. Denault AY, Couture P, Buithieu J, Haddad F, Carrier M, Babin D, Levesque S, Tardif JC. Left and right ventricular diastolic dysfunction as predictors of difficult separation from cardiopulmonary bypass. Can J Anaesth 2006;53:1020–9
4. Michaux I, Filipovic M, Skarvan K, Schneiter S, Seeberger MD. Accuracy of tissue Doppler estimation of the right atrial pressure in anesthetized, paralyzed, and mechanically ventilated patients. Am J Cardiol 2006;97:1654–6
5. Haddad F, Couture P, Tousignant C, Denault AY. The right ventricle in cardiac surgery, a perioperative perspective: I. Anatomy, physiology, and assessment. Anesth Analg 2009;108:407–21
6. Tumuklu MM, Erkorkmaz U, Ocal A. The impact of hypertension and hypertension-related left ventricle hypertrophy on right ventricle function. Echocardiography 2007;24:374–84
7. David JS, Tousignant CP, Bowry R. Tricuspid annular velocity in patients undergoing cardiac operation using transesophageal echocardiography. J Am Soc Echocardiogr 2006;19:329–34
8. Tousignant CP, Bowry R, Levesque S, Denault AY. Regional differences in color tissue Doppler-derived measures of longitudinal right ventricular function using transesophageal and transthoracic echocardiography. J Cardiothorac Vasc Anesth 2008;22:400–5
9. Tei C, Dujardin KS, Hodge DO, Bailey KR, McGoon MD, Tajik AJ, Seward SB. Doppler echocardiographic index for assessment of global right ventricular function. J Am Soc Echocardiogr 1996;9:838–47