Diagnostic Accuracy and Therapeutic Impact of Transthoracic and Transesophageal Echocardiography in Mechanically Ventilated Patients in the ICU

Diagnostic Accuracy and Therapeutic Impact of Transthoracic and Transesophageal Echocardiography in Mechanically Ventilated Patients in the ICU* Philippe Vignon, M .D.; Herve Mentec, M.D .; Sylvie Terre, M.D .;! Herve Gastinne, M .D.; Pascal Cu eret , M.D. ; and Francois Lemaire, M .D. Study objectives: To assess the respective diagnostic accuracy of transthoracic echocardiography (TIE) and transesophageal echocardiography (TEE) and their therap eutic implications in mechanically ventilated patients, in the intensive care unit (ICU). Design: A prospective study. Se ttings: Intensive care units of two tertiary ref erral teaching hospitals. Patients: One hundred eleve n ICU patients (81 men and 30 women; mean age 57 ± 16 years). Fifty-seven percent we re hospitalized for medical illn esses, 16.5 percent after thoracic surgery, 10.5 percent after other surgery, and 16.0 percent for multiple trauma. Th eir Simplified Acut e Ph ysiolo gic Score was 16±5. Inter ventions: Th e echocardiograms were performed in ord er to solve well-defin ed clinical problems. TIE wa s th e first step of th e procedure and TEE wa s performed onl y when (1) TIE did not solve the clinical problems, and (2) TIE yielded unsuspected findings requiring TEE. During each echocardiographic study, the follow ing were noted: ventilatory mode, clinical problems, imaging quality, results, con sequence on acute care, duration of the procedure, and potential complications of TEE. Diagnostic accuracy wa s defined as the proportion of solved problems , and therapeutic impact was defined as changes on acute care that resulted directly from th e procedure. Measurements and Results: On e hundred twenty-eight consecutive TIE and 96 TEE were performed. TIE solved 60 of 158 clinical problems (38 percent), whether positive end-e xpiratory pressure (>4 em H20) was

present or not (28 of 74 vs 32 of 84: p>0.50). TIE allowed evaluati on of left ventricular function in 77 percent of ca ses and pericardial effusion in every case, but it did not solve most of the other clinical problems. Indeed, the diagnostic accuracy of TEE was markedly superior (95/98 vs 60/158: p
E ch ocardiography is a nonin vasive procedure th at sim ultaneously yields m orphologic a nd hemod yn amic in formation. Because of ve rsa tility, safe ty, a nd instantan eous diagnosti c ca pability , ec h oca rd iog ra phy is an att ractive imaging technique in th e inten sive care unit (ICU) setti ng . Nevertheless, goo d

im aging quality and th e presen ce of a train ed ec hocard iog ra p her a re esse n tial for a n ac curate diag nos is. The d e velopment of transthoracic ech oca rd iog ra p h y (T T E ) has co n tri b ute d to th e care of critically ill patients for se veral yea rs. 1,2 Howe ver , numerous restrictions on the imagin g ability of TTE-particularly m echanical ve ntila ti on wit h posit ive en d -ex p irator y pressure (P E E P)- a re common ly present in patients in th e ICU . Less hampered b y these limitations , transesophageal ec hocard iog ra phy (T E E), wh ic h has been available to inten sivists for sev eral years, provides high-quality im ages and allows ex-

*From the Dep artm ent s of Intensive Ca re (Drs. Vigno n and Gasti nne) and Ca rdio logy (Dr. C ueret), Dupuytr en hospital , Lim oges, Fran ce; and the Departmen t of Med ical Intensive Ca re (Drs. Ment ec an d Lemai re ), Henri Mondor hospita l, Cre teil, France. [ Deceased . Manuscript received December 8, 1993; revision acce pted Mar ch 25, 1994.

PEEP=positive end-expiratory pr essure; TEE= transesophag eal echoca rd iogra phy;TT E = trans thor acic echocardiography

Key words: echocardiography; intensive care unit ; mechanical ventilation; transesoph ageal echocardiography

CHEST / 106/ 6/ DECEMBER, 1994

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amination of deep cardiovascular structures that are inaccessible via the transthoracic approach.f The benefits of TEE in the ICU setting have been mainly extrapolated from experience in cardiology.? Few prospective studies have evaluated the contribution of TEE to the treatment of critically ill patients.v" However, the diagnostic accuracy and the therapeutic impact of echocardiography in ventilator-dependent patients remain largely unknown. This prospective study was undertaken to evaluate the respective diagnostic accuracy and impact on acute care of TTE and TEE in mechanically ventilated patients in the ICU. METHODS

Patients

The study was carried out from July 1992 to July 1993 in the ICUs of two tertiary referral teaching hospitals (the medical ICU of Creteil from July 1992 to November 1992, the lCU of Limoges from November 1992 to July 1993). All consecutive mechanically ventilated patients who underwent an echocardiogram during this period were included in the study, unless TEE was contraindicated. 4.9 Echocardiography

The request for echocardiography emanated from the attending physicians who adressed well-defined clinical problems relating to the patient's clinical status . Severalclinical problems might need to be solved in a single patient. Examinations were performed by three ICU specialists trained in echocardiography (P.V., H.M., S.T.). Transthoracic echocardiography was performed prior to the transesophageal approach, even when examination conditions were unfavorable. Transesophageal echocardiography was performed when (1) the clinical problems could not be solved by TTE because of suboptimal quality or nonvizualization of certain cardiovascular structures, and (2) TTE yielded unsuspected findings requiring TEE, according to cardiologic experience.S'' Echocardiographic examinations were performed with one of two machines (Hewlett-Packard Sonos 500 or a Ving Med CFM 750). A standard 2.5-MHz ultrasound transducer for the transthoracic studies and a single plane 5-MHz transesophageal probe for the transesophageal examinations were used. Echocardiographic studies wer e performed in supine position as previously descrlbed .v'' Unless the patients were previously sedated, midazolam (0.10 to 0.15 mg /kg) alone or with vecuronium bromide (0.10 mg /kg) was intravenously administered before TEE probe introduction. When present, the nasogastric tube was not removed. No antimicrobial agent for endocarditis prophylaxis was adminlstered.l? Throughout the TEE examination, the blood pressure , heart rate, and oxygen saturation were monitored. Analysis

For each echocardiographic study, the following data were recorded: ventilatory mode, diagnostic problems, imaging quality, results, consequence on acute care, duration of the physician's presence, and potential complications of TEE. Diagnostic problems were considered as solved when echocardiography yielded a positive or a negative result without equivocal findings. Diagnostic accuracy of TTE and TEE was defined as the proportion of solved problems, and therapeutic impact was defined as changes in acute care that resulted directly from the procedure. Data were expressed as mean values ± SD. The X2 test and

1830

Student's t test were used for statistical analysis. A p value <0.05 was considered significant. RESULTS

During the study period, 175 consecutive echocardiographic examinations were performed in 153 patients in the ICU . Forty-four procedures performed in 39 spontaneously breathing patients were excluded. Three contraindications to the use of TEE were noted (one esophageal surgery, two esophageal bleedings). Finally, 128 TTE and 96 TEE examinations were performed in III mechanically ventilated patients to solve 158 clinical problems. Fifty-seven percent of patients were admitted to the ICU for medical illnesses, 16.5 percent after thoracic surgery, 10.5 percent after other surgery, and 16.0 percent for multiple trauma. The male to female ratio was 2.7 and mean patient age was 57 ± 16 years (range, 16 to 81 years) . Their Simplified Acute Physiologic Score (SAPS) was -Ifi zt f (range, 6 to 28).

TTE Evaluation Among 128 procedures, imaging quality was good in 70 cases (55 percent), suboptimal in 30 cases (23 percent), and poor in 28 cases (22 percent). TTE solved 60 of 158 clinical problems (38 percent) (Fig 1). The assessment of left ventricular function and the Clinical problems" (n = 158)

Problems solved ~'------TTE (n

= 60)

Problems non solved (n = 88)

Unsuspected

fmdings

(n = 10)

TEE

/~

Problems solved (n = 95)

Problems non solved ( n = 3)

• One patient might undergoan echocardiogmm for severalclinical problems

FIGURE 1. Diagnostic accuracy of transthoracic (TT E)and transesophag eal (TEE) echocardiography. Diagnostic accuracy was defined as the proportion of solved problems.

Diagnostic Accuracy and Therapeutic Impact of TTE and TEE in MVPatients (Vignonet aQ

Table I-Diagn ostic Accuracy of Tra nst ho racic Ec hoc ardiographq (ITE) According to th e Clinical Problems (n= I58) in M echanically Ventilated Pati ents in th e Intensive Care Unit (N=I ll)

Cli nical Probl em s Left ventric ular funct ion Shoc k, hypotcnsion Endoca rd itis T raum ati c ruptur e and acut e d issection of the aorta Valvulopat hy a nd valvu lar pro sthesis assessme nt Assessment of a card iopathy aft er ca rd iac arrest Pericardi al effusion Pul monar y hyperte nsion, thr om bus in rig ht chambe rs Systemi c arte rial em bolism Ventricul a r assista nce device Paten t foram en ova Ie Atrial co m pression by postope rativ e hem at om a Tum or of the medi astin um Total

Prob lem s Solved by TIE Alone/ Ov erall No . of C linical Problem s 3 1/ 40 6/ 25 1/1 9 0/ 16 4/1 6 5/11 10/10 3/8 0/4 0/4 0/ 3 0/1 0/ 1 60/ 158 °

*On e patient m ight under go an echoca rdiogra phy for severa l clinica l probl ems.

detect ion of peri cardiaI effusion was ac hieved in, respect ively, 77 percent and 100 per cent of cases (T able 1). Th e pr esenc e of PEEP (> 4 em H20) d id not influence the ability of TT E to solve clin ical problem s (28 of 74 vs 32 of 84: p>0.50). TT E had an impact on clinical managem ent in 16 per cent of cases (20/ 128) and th erapeutic changes consisted usually in ad m inistering catecholamines intra venously or in fluid expansion (Ta ble 2). Tw o pat ient s with br ain death ad mitted as heart donors under went surger y based on TTE findings, and pericardioccntesis was per form ed in one patient under TTE control. Th e mean durati on of ph ysician presence was 27 ± 12 min (range , 5 to 60 min ).

TEE Evaluatio n Nine ty-six TE E examina tions were performed . Imaging q uality was good in 69 cases (72 per cent ), suboptimal in 24 cases (25 percent), and conside red as poor in only 3 cases (3 per cent ). TEE solved 95 of 98 clinica l problem s (97 pe rce nt) (Fig 1). On three occasions, T EE was unable to solve the diag nostic pro blem : th e etiology of mild mit ral regurgit ati on (chordal disruption or vege ta tion), suspicion of tr icuspid endocarditis (nonvizualization of th e tr icuspid valve becau se of a d ilated ascendi ng aorta) , and suspicion of traumatic rupture of th e aorti c isthmus (suboptimal qu alit y attributed to the presence of air in the med iastinum). TEE had a th er apeutic impact

in 36 per cent of procedures (35/ 96), prompting surgical int er vention without any addi tiona l investigations in 8 pati ents (T able 2). The mean duration of physicia n pr esen ce was 43 ± 17 min (range 15 to 135 min). No complica tion of TEE was noted and hemod yna mic tolerance, in pa rtic ular, was fairly good .

T T E vs T EE Among th e 128 tr ansthoracic ec hoca rdiogra phic exam inations, 96 were followed by a tr an sesoph ageal exa mina tion. Th e diagnostic acc uracy of T EE was grea ter th an that of TT E (95/98 vs 60/ 158: p
Conven tional ec hoca rd iogra phy is he lpful in th e trea tmen t of pati ents in th e IC U;2 however , one third to one half of all mech ani cally ventila ted pati ents cannot be studied satisfac torily.' Our results confirm th is find ing since 55 per cent of th e TTE examinations were inconclusive due to poor imaging qualit y, explaining its poor diagnostic accuracy (38 per cent). The diagnostic capacit y of TT E, however , was not altered by th e presen ce of PE EP . In pr evious stud ies, 7,1 1 high er rates of diagn ostic acc urac y hav e been reported . These di fferences are not surprising, conside ring th at most of those pati ents wer e spontaneously breathing.U! It is noteworthy that TTE was Tabl e 2-Therapeutic Impact of Tran sthora cic (ITE) and Tran sesophageal Ec hocardiogra pluj (TEE)* Th er apeutic Changes Ca techolam ines infusion Fluid cha llenge Rapid ca rdiovascular surgery Anticoag ulation or fibrin olytic agen ts Antibio tics for endoc ard itis t/-blockers Perica rdi ocent esis Total

(n = 21) (n = 18) (n= lO) (n = 2) (n = 2) (n = l) (n = l) (n = 55 )

TEE (n = 128)

T EE (n = 96)

10

11 (1) 12 (4) 8 1 2

6 2 1

o o 1 20

1

o 35

"T her a peutic impact was defined as c hanges on acu te care that result ed dir ect ly from the pro cedu re. T herapeutic changes based on TT E findings and confirmed by TEE in the sa me pa tients a re ind icated in pa rent heses. CHEST 1 106/ 61 DECEMBER, 1994

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Table 3- Trans thorac ic (ITE) vs Transesophageal (TEE) Ech ocardiographic Findings According to th e Clinical Problems (n =98) in Pati ents Who W er e Sc hedu led f or Both Examination s (n=96)

Diagnosis Ruled Out No by TEE Superiority and Not of TEE Excluded Over TIE by TIE

Clinical Problems Shock, hypotension Endocarditis Traumatic rupture of the aortic isthmus, acute aortic dissection Valvulopathy or valvular prosthesis assessment Left ventricular function Assessment of a cardiopathy after cardiac arrest Pulmonary hypertension, thrombus in right chambers Systemic arterial embolism Ventricular assistance device Patent foramen ovale Atrial compression by postoperative hematoma Tumor of the mediastinum Total

(n=19) (n=18) (n=16) (n=12) (n=9) (n=6) (n=5) (n=4) (n=4) (n=3) (n=l ) (n=l) (n=98)

0 1 1 0 0 0 0 0 0 0 0 0 2

2 10 10

3 5 2 4 2 2 2 1 1 44

Additional Additional Diagnosis Yielded Diagnosis Yielded by TEE by TEE With Without Therapeutic Therapeutic Impact Impact* 4 4 1 5 1 3 0 1 2 1 0 0 22

13 (2) 3 (2) 4 (3) 4 (1) 3 1 1 1 0 0 0 0 30

*The number of patients who underwent cardiovascular surgery based on TEE findings are indicated in parentheses. valuable in th e assessm ent of left ve ntricular systolic fun cti on and pericardial effusion in th e curre nt study (Table 1). This is probabl y d ue to th e fa ct that the subcosta l view (long and sho rt axis), which can be performed in most patient s, pr ovides pr eci ou s informati on , particularly co ncern ing chambe r size , allowing ventricular fun cti on assessment and path ophysiologic stud ies.l'' Conversely, we had to use transesoph ageaI exploration to solve othe r cli nica l problems in th e majority of cases (F ig 1), because th e imaging quality of TTE was suboptimal or poor , or bec ause ce rta in ca rd iovascular stru ct ures we re not visualize d . It was thus nec essary to perform T E E in 75 per cent of cases, where as in card iologic practice 5 to 10 percent of pati en ts who undergo TTE require TEE .I3 In our study, T EE ha d a high di agn ostic acc ur acy (97 per cent), sim ilar to that reported by Pa vlides et al ll (95 per cent) in awak e patients in card iology. The proxim it y of the esophageal pr obe to th e post erior card iac structures allows high -q uality im aging, wh ich is less affec ted by breathin g, and accounts for th e high diagn ostic accuracy of T EE in m ech anically ventila ted patients. H owever , three clinical problems cou ld not be solve d by T E E. No ne of these un answered q uestions were solve d by TTE. The use of bipla ne or m ultiplane TEE wo uld probably ha ve been a crucial tool in th ese cases. 14,15 To our kn owledge , no prospective st udy has clearly demonstr at ed the supe rior ity of T E E ove r TTE co ncerning d iagn ostic accuracy a nd th erapeutic manage ment of patients in th e IC U recei ving m ech anica l ventila tion . However , Oh et a l5 reported the value of T E E in ICU settings w hen co nventio nal echocardiogra ph y was of suboptimal qualit y , and other au tho rs7,8 dem onstrated th e su pe rio rity of TEE over 1832

TTE in critically ill patients in who m th e wide ma jority we re spontan eously breathing. In th e current stud y , whe n m echanically ve ntila te d patients we re ref erred for both TTE and TEE, the transesophageal procedure yielded an addi tiona l diagn osis or excl uded a suspected di agnosis th at co uld not be excl uded by TTE, th erefore avo id ing further invasive investi gations and potentiall y harmful th erapy ; in only 2 percent of cases , T E E had no su pe ri ority over TTE (Table 3). Nev erthel ess, we certainly ove restim ate d the su pe rio ri ty of TEE over TTE , beca use we did not take into account th e number of transth or acic examinati ons that we re not followed by TEE (Table 1). In the present stud y, T E E ap peare d essential for th e evaluation of hypoten sion or shoc k, as reported elsewhe re.f Indeed, TEE had a th erapeutic im pact in two thirds of all patien ts exam ine d for shock (Table 3). Hen ce , we ag ree wit h severa l authors5,16- 19 who ha ve pointed out th e value of T E E in det ermining th e cause of shock. Furthermore , TEE is useful in det ecting postoperative com plicatio ns of cardiac surgery .5,18,20 Indeed, precordial windows are fr equently inaccessible in suc h situa tions, as in one of our pati ents under ve ntricula r assista nce w ho developed ca rd iac tamponade.S! The gra de of mitral in sufficiency was also underestimat ed by TTE in one patient with card iogenic shoc k and in another wit h pulmonary edema. In th ese cases, TEE esta blishe d th e di agn osis by visualizing m assive mitral regurgitation , det ermin ed its etio logy, and prompted surgica l intervention. O th er reports7,8,22 have demonstra ted th e superiority of T E E in th e assessment of m itral valve disease in cri tically ill patients. T EE was extremely valua ble in th e ev aluation of

Diagnostic Accuracy and Therapeutic Impact of TIE and TEE in MV Patients (Vignon et al)

endocarditis, since it always yielded additional information as compared with TTE except in one case, and allowed us to confidently exclude this diagnosis in the remaining patients (Table 3). These results are consistent with previous observations in patients in the rcu7,8 and in concordance with several cardiologic studies that demonstrated that TEE has higher specificity and sensitivity in detecting leaflet vegetations,2S abscesscs.P' and vegetations on prosthetic valves.25 However, TEE was inconclusive in two of our cases as has been previously reported in awake patients.ll The third main indication of TEE in th e pr esent study was suspected acute injury of the thoracic aorta. Although proximal aortic dissectlonv? and traumatic rupture of isthmus26,27 may be diagnosed by the transthoracic approach, TTE never solved this clinical problem (Tabl e 1). TE E was superior to TTE in all but one case, since it diagnosed two cases of traumatic rupture of the aortic isthmus prompting rapid surgical intervention without further investigations, and excluded this life-threatening injury in th e remaining patients with multiple trauma (Table 3). It appears that TEE is becoming th e method of choice in diagnosing dissection of the thoracic aor ta;28 howev er , its place in the management of a suspected traumatic rupture of the aorta remains to be defined .29 Lastly, TEE was superior to TTE in solving the other diagnostic problems (Tabl e 3), as previously reported.P Echocardiography can establish an immediate diagnosis at th e patient's bedside with potential therapeutic implications. It appears that patient treatment is mor e frequently modified by echocardiographic findings in rcu settings than it is in the cardiology department. Indeed, Pavlides et all! reported that therapy was modified in 10 percent of patients following TTE and 23 per cent after TEE as compared with 16 percent and 36 perc ent, respectively, in our study. Even when the principal changes in treatment were medical, both TTE and TEE led to cardiovascular surgery without additional more invasive and time-consuming investigations in ten patients (9 percent) . This reduced delay in making therapeutic decisions is of utmost importance in unstable critically ill patients. Moreover , in one of our patients , the pericardiocentesis was guided by TTE, which enhanced the efficacy and safety of the proc edure, as pr eviously reported .P" Transesophageal echocardiography has been demonstrated to be a safe procedure in a large numberof patients, since significant complications occur in only 0.18 to 0.50 percent of examinations,Sl,S2 usually in spontaneously breathing patients. These consist of bronchospasm, laryngospasm , or pulmonary ede ma

leading to hypoxia, arrhythmias and atrioventricular block, hypotension, bleeding com plications, and vomiting. Mortality rate is extreme ly low , less than 0.05 percent. Thus, one case of fatal hematemesis due to malignant tumor''! (1/10,218 examinations) and one case with cardiac arrest that could not be successfully ressucitated'F (1/ 2,049 procedures) have been previously reported . However , the safety of TEE in patients in the ICU is not yet well documented. In this study, neither per sistant hypox emia'' nor hypotension" was noted . Furthermore, the observed changes in blood pressure, heart rate, and oxygen saturation were not clinically relevant. In conclusion , when performed by an exp erienc ed echocardiographer to avoid numerous pitfalls,s3 TEE's diagnostic accur acy and therapeutic impact ar e markedly superior to that of conventional TTE in mechanically ventilated patients, in the ICU, although TEE requires a ph ysician's pr esence longer. This well-tolerated valuable diagnostic technique appears essential in an rcu setting where TTE is often of suboptimal quality and may therefore lead to false-n egative results . Left ventricular function and pericardial disease, however , can be evaluated by TTE in most mechanically ventilated patients, even with PEEP. Lastl y, th erapeutic changes occur in almost 25 perc ent of cases. Th e anticipated use of that biplane and multiplane transesophageal probes will further enhance usefulness of this imaging technique in routine ICU practice. ACKNOWLEDGMENTS: This work is dedicat ed to the memory of Sylvie Terr e. We are indebt ed to Pr. J. Bensaid, Dr. P. Lagran ge, Dr. O. Abrieu, and to our colleagues of the Cardiology Department of Limoges hospital for their cooperati on. We gratefully thank Catherine Balaguer for her expert assistance in the preparation of this manuscript. R EFERENCES

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Diagnostic Accuracy and Therapeutic Impact of TIE and TEE in MV Patients (Vignon et all