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lectrocardiographic Manifestations ofPulmonary mbolismEDWARD ULLMAN, MD, WILLIAM J. BRADY, MD, ANDR EW D. PERRON, MD,THEODORE CHAN, MD,1- AND A MA L MA I-I-U, MD::I:

The electrocardiogram (ECG) may be entirely normal in the patient withpulmonary embolism (PE); alternatively, any number of rhythm and/ormorphologic abnormalities may be observed in such a patient. Theabnormal ECG may deviate from the norm with alterations in rhythm, inconduction, in axis of the QRS complex, and in the morphology of the Pwave, QRS complex, and ST segment/T wave. The electrocardiographicfindings associated with PE are numerous, including arrhythmias (sinustachycardia, atrial flutter, atrial fibrillation, atrial tachycardia, and atrialpremature contractions), nonspecific ST segmen t/r wave changes, Twave inversions in the right precordial leads, rightward QRS complexaxis shift and other axis changes, 1Q3 or S1Q3T3 pattern, right bundlebranch block, and acute cor pulomnale. This review focuses on the ECGand the various abnormalities seen in the patient with PE. (Am J EmergMed 2001;19:514-519. Copyright ~ 2001 by W.B. Saunders Company)

The d iagnos i s o f pu lmonary embol i sm (PE) re li e s p re -dom inant ly on the magn i tude o f c l inical suspicion and, a tthat level of suspicion, the interpreta t ion of diagnos t ic in-ves t igat ions . Reports have shown that less than 50% ofpulmonary embol i are diagnosed a t presentat ion. The ra te ofd iagnos i s i s more pronounced in the e lde r ly popula t ion- -less than 30% of PE are diagnosed on the index vis i t . 1 Man ystudies have shown that acute onset of dyspnea, pleuri t icpain, tachy pnea, ches t pain, and hemo ptys is 2,3 are s igns ofPE. As with mo st c lass ic sym ptom cons te l la t ions , thesescomplaints rare ly occur s imul taneous ly. A myriad of tes tsmay be performed including ches t radiography, 12-leadelect rocardiogram (ECG), and ar ter ia l blood gas to furtherinves t igate the c l inical pic ture . The ECG is of ten an ini t ia ldiagnos t ic tes t performed. As e lect rocardiographic changeshave been noted in the PE pat ient , i t i s important to recog-nize and unders tand the abnormal i t ies . An addi t ional indi-cat ion of the importance of the ECG is that the majori ty ofelectro cardio grap hic m anife station s are transient.4, 5

The ini t ia l e lect rocardiographic f inding of PE was f i rs treported in 1935 by M cGin n and Wh ite 6 who noted w hat isnow the t radi tional S 1Q3T3 pat tern in acute cor pulm onale .Subsequent reports have described many f indings rangingf rom s inus t achyca rd ia and minor ST segment -T wave ab-normal i t ies to r ight axis deviat ion, t rans ient f ight bundlebranch b lock (RBBB) , and inve r t ed T waves . 7 The re la -

From the Department of Emergency Medicine, University of Vir-ginia, Charlottesville, VA; the 1-Department of Emergency Medicine,University o f Califo rnia San Diego, San Diego, CA; and th e :l:Depart-ment of Emergency Medicine, University of Maryland, Baltimore,MD.Manuscript received and accepted February 28, 2001.Reprints are no t available.Key Words Electrocardiogram, pu lmon ary emb olism.Copyright 2001 by W.B. Saunders Company0735-6757/01/1906-0012535.00/0do i:l 0.1053/ajem.2001.27172514

t ively low sens i t ivi ties of these various e lect roca rdiographicpresentat ions , however, l imi t the abi l i ty to use the tes t as asole diagnos t ic tool . Twenty-one different e lect rocardio-graphic manifes ta t ions of PE are discussed in the medicall i tera ture; only a minori ty of these f indings , however, areactual ly useful to the c l inic ian in es tabl ishing a d iagnos is o fPE. Electrocardiographic changes are bes t seen in thosepat ients wi th m ass ive or subm ass ive em bol izat ion. 8 Studieshave shown tha t 15% to 27% of EC G were normal . 4 Themos t com mon abnormal i ti e s a re nonspec i fi c ST segment -Twave changes wi th s inus tachycardia , unfortunately, thesefindings are ex trem ely nonsp ecific. 6.9C A S E P R E S E N T A T I O N SC ase 1

A 54 year-o ld man with a his tory of recent or thopedicsurgery presented to the ED complaining of sudden dys-pnea. On examinat ion, he appeared in moderate dis t ressbecause of dyspnea. His vi ta l s igns included a pulse of 125beats /min. , respira tory ra te 36 breaths /min, pulse oximetry92%, and b lood pres sure 165/90 mmHg. Hi s examina t ionwas unremarkable except fo r a lower ex t remi ty which wascas ted. The pat ient was placed on a cardiac moni tor and anECG was obtained (Fig 1) , showing s inus tachycardia . Thecl inical suspicion for PE was very high, resul t ing in avent i la t ion/perfus ion (V/Q) scan which was reported ash igh probabi l i ty fo r pu lmonary embol i sm.C ase 2

A 64-year-old woman with a his tory of diabetes andhypertens ion presented to the ED complaining of shortnessof b reath . On examina t ion , she appea red comfor t ab le andaler t . Vi ta l s igns showed a normal temperature , pulse 110beats /min, respira tory ra te 32 breaths /min, pulse oximetry97% on 5 l i ters oxygen, blood pressure 163/107 mmHg. Herexamina t ion was o the rwise unremarkable . An ECG wasobtained (Fig 2) , reveal ing inverted T waves in the r ight tomid precordial dis t r ibut ion ( leads V1 to V4). Ches t radiog-raphy was normal . A V/Q scan was obtained, reveal ing a

high probab i l i ty scan.C ase 3

A 52-yea r -o ld woman wi th a h i s to ry of deep venousthrombos i s (DVT) presen ted to the ED compla in ing of 3days of dyspnea and l ightheadedness . On examinat ion, sheappeared comfortable and a ler t wi th vi ta l s igns as fol lows:pulse 105 beats /min, respira tory ra te 26 breaths /min, pulseoxime t ry 91%, and b lood pres sure 110/70 mmHg. Theremainder o f he r examina t ion was no tab le on ly for a swol -

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FIG UR E 1. Case 1, Sinus tachycardia.. . . . . 7 ; ;

FIG UR E 3. Case 4, Righ t bundle branch block.

len, tender lower extremity. An ECG was obtained, showingan s inus tachycardia wi th prominent S waves in lead 1 andaVl . A V/Q scan was low probabi l i ty . With the c l inic ian 'shigh level of suspicion for PE, a lower extremity ul t rasoundrevealed evidence of DVT. This f inding, coupled with thecl inical suspicion for PE, prompted a pulmonary angiogram,conf i rming the d i agnos i s o f pu lmon ary em bol i sm.Case

A 2Q-year-old man with a his tory of hypertens ion p re-sented to the ED with dyspnea, pleuri t ic ches t pain, andcough prod uct ive of blood-t inged sputum. O n arr ival , thepat ient ' s temperature was 100.6F, pulse 110 beats / ra in,respira tory ra te 30 breaths /min, pulse oximetry 91%, andblood pres sure 140/90 m mHg . Hi s examina t ion was no tab lerespira tory dis t ress and a swol len lower extremity. The EC Gwas obtained (Fig 3) and showed s inus rhythm with newRBBB pat tern. The ches t radiograph was otherwise unre-markable . The V/Q scan was h igh probabi l i ty fo r PE .Case 5

A 2Q -year-old man without pas t medica l his tory pre-sented to the ED with dyspnea, cough, and ches t pain. Thephys ica l examina t ion was normal w i th the except ion of arapid pulse of 140 beats /min no ches t wal l tenderness wasfound. A 12-lead ECG (Fig 4) revealed norm al s inus rhythmwith the S1Q3T3 pat tern. A V/Q scan was performed witha high probab i l i ty result .Case 6

A 42-yea r -o ld man wi th no pas t medica l h i s to ry pre -s en ted v ia ambulance to the ED wi th dyspnea and ches t

pain. On further review of the his tory, i t was determinedthat the pat ient was not experiencing dyspnea but fe l t anincrease in the pain on inspira t ion which l imited respira t ion.The examinat ion revealed a middle-aged pat ient in cons id-erable dis t ress , c lutching his ches t ; the remainder of theexaminat ion was unremarkable . A 12-lead ECG (Fig 5)showed s inus rhythm with the S1Q3T3 pat tern. The ches trad iograph was normal . A V/Q scan was pe r formed wi th a

low probabi li t y re su lt p rompt ing a pu lmonary angiogramwhich d id no t revea l PE . No ev idence of PE was found inthis pat ient . He was diagnosed with a musculoskeleta lsource of his pain. A prior ECG was obtained which re-vealed s imilar f indings , including the S1Q3T3 pat tern.DISCUSSION

P u l m o n a r y t h r o m b o e m b o l i s m m o s t c o m m o n l y o c c ur s a sa compl i ca t ion of venous th rombos i s , p r imar i ly f rom c lo t slocated in the deep veins o f the low er extremit ies and pelvis .These c lots dis lodge fro m their or igin and t ravel through thevenous c i rcula t ion to the pulmonary ar tery. The format ionof venous th rombos i s i s usua l ly caused by one or more ofthe fol lowing factors : endothel ia l injury, hypercoagulabi l -i ty, or s tas is of blood. C om mo n cl inical s i tuations associ-a t ed wi th inc reased r i sk of p rox ima l deep venous th rombo-s is include conges t ive heart fa i lure , myocardial infarct ion,immobil izat ion (pos tsurgical , bed res t , s t roke, prolongedtravel) , mal ignancy, pregnancy, es t rogen therapy, obes i ty,and pr io r DVT.The degree of obs t ruc tion s econdary to the embol i sm i sdirect ly re la ted to the response of the r ight ventr ic le to thePE and, therefore , the c l inical manifes ta t ions , including the

FIGU RE 2. Case 2, T wave reversions in leads V1 to V4. FIGU RE 4. Case 5, Sinus tachycardia with SIQ3 T3 pattern.

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516 AMERICAN JOURNAL OF EMERGENCY MEDICINE Volume 19 Number 6 October 2001

FIGUR E 5. Case 6, Norm al sinus rhythm with S1Q3T3 patternnot related to PE.

e l e c t r o c ar d i o g r a p h i c a b n o r m a l i t i es . T h e e m b o l i s m l i k e lycauses a re l ease of vasocons t r i c t ive fac tors such a s s e ro-ton inS ; ca t echolamines may a l so p l ay a ro l e in the pa tho-phys io lo g ic re sponse . 8 As no ted in the cases p resen ted ,the ma jor i ty o f f ind ings po ten t i a l ly use fu l t o the c l in i c i anresu l t f rom the r igh t - s ided hea r t s t ra in pa t t e rn . The in -c rease in r igh t - s ided hea r t p res sures c rea t e s an inc reasedr igh t ven t r i cu la r a f t e r load , re su l t ing in inc reased r igh t -s ided myocard ia l wa l l t ens ion . As the r igh t ven t r i c l e i sno t phys io log ica l ly capable to w i ths t and such pres sures ,i t r ap id ly d i l a t e s , w i th an inc rease in chamber s i ze andeventua l con t rac t i l e dys func t ion . The f ina l ca rd iac i s suein th i s pa thophys io log ic cascade i s a reduc t ion in r igh thea r t ca rd iac ou tpu t ( i e , a reduc t ion the pre load for thel e f t ven t r i c l e ) which u l t ima te ly produces a dec rease inl e f t hea r t ca rd iac ou tpu t . 8 The reduced ca rd iac ou tpu tc o m p r o m i s e s b o t h s y s t e m i c a n d c o r o n a r y p e r f u s io n . U n -de r normal phys io log ic condi t ions , r igh t - s ided pe r fus ioni s cons tan t t h rough bo th sys to l e and d ia s to l e ; t he inc reasein wa l l t ens ion cou pled wi th the sys t emic hypotens ion ,however, increases the poss ibi l i ty of r ight-s ided myocardialischemia and infarct ion. As r ight-s ided ventr icular dysfunc-t ion worsens , r ight ventr icular infarct ion and c i rcula toryco l l apse may occur>

The ECG may be ent i re ly normal in the pat ient wi th PE;a l t e rna t ive ly , any number of rhy thm and/or morpholog icabnormal i t ies may be observed in such a pat ient . The ab-normal EC G may dev ia t e f rom the norm wi th a l te ra tions inrhythm, in int ra- and interventr icular conduct ion, in axis ofthe QRS com plex , and in the mo rphology of the P wave ,QRS complex, and ST segment /T wave. The e lect rocardio-graphic findings associated with PE are numerous, includingarrhythmias (sinus tachycardia, atrial flutter, atrial fibrillation,atrial tachycardia, and atrial premature contractions), non spe-cific ST segment/T wave changes, T wave inversions in theright precordial leads, rightward QRS complex axis shift andother axis changes, S1Q3 or S1Q3T3 pattern, RBBB, madacute cot pulomnale defined by S1Q3T3 pattern, right axisdeviation , and RB BB . I,1~

Regard ing the normal ECG, i t i s meant to be com-ple t e ly normal - - s inus rhy thm be tween 60 and 100 bea t s /ra in wi th normal conduct ion, axis , and P wave, QRS com-plex , and ST segment /T wave morpholog ies . An en t i re lynormal ECG has been found in approxima te ly 10% to 25%

of P E patients. 12,13 Interestin gly, a not insignificant nu mb erof such pat ients wi l l cont inue to manifes t a normal ECGduring hospitalization . 14Sinus tachycardia is the most frequent rhythm encoun-tered on presentat ion to the ED in the pat ient w i th PE. 6,9 Therate of the s inus tachycardia is usual ly between 100 to 125beats /min as seen in Fig 1; a lternat ively, in the pat ient wi tha large c lot burden (s ignif icant r ight ventr icular obs t ruct ionand/or hypox emia) , the ra te ma y be very rapid as seen in Fig4. Sinus tach ycardia in the face o f PE is l ikely re la ted to thephysiologic demand to increase cardiac output . As lef t -s ided s t roke volume decreases , heart ra te must increase tomaintain cardiac output . Atr ia l arrhythmias , part icular lyatrial fibrillation and atrial flutter, are also seen in the acutePE pat ient ; these dis turbances l ikely resul ts from atr ia lenlargement (Fig 6) .RBBB (Figs 3, 7, and 8) , e i ther complete or incomplete ,is found in pat ients wi th PE; i t s incidence is variable ,ranging from a low of 6% to as high as 67%. 14 A m orereal is t ic f igure is approximately 25% of those wi th PE wil lshow this pat tern on presentat ion. The PE-rela ted RBBBpat tern is t rans ient , of ten resolving with the res torat ion ofnormal r igh t - sided ca rd iac hem odyna mic pa ramete rs ; i t maybe pers is tent, though s t il l ul t imately resolving 3 m onths to 3years af ter the index PE. 12 While RBB B is sugges t ive o f PE,i ts presence is s t i l l nonspecif ic and therefore not diagnos-t ic. 9.15 RBB B ma y also be associa ted with ST segm entelevat ion and prominent , upright T w aves in lead V1 and/orV2, potent ia l ly mimicking anter ior or pos ter ior infarct pat -ter n. ~4Right , lef t , and indeterminant QRS axis changes havebeen reported in acute PE pat ients . Al though r ight axisdeviat ion (RAD) is described as the c lass ic axis changeassociated with PE, lef t axis deviat ion (LAD) actual ly oc-curs m or e ofte n. 12.14.16.17 Pre -ex istin g dis ease m ay alsoimpact the axis deviat ion on presentat ion in the ED as seenin the Urokinase -Pulmonary Embol i sm Tr i a l (UPET) . Inthis t r ia l , the inves t igators report that LAD occurred morefrequent ly than RAD in the PE s tudy populat ion. Whenthose individuals wi th pre-exis t ing cardiopulmonary diseasewere exc luded , t he inc idence of LAD and RAD was equiv-alent.15

Increase in the P wave ampli tude greater than 2.5 mV inlead II , known as P-pulmonale , has been c lass ical ly associ-

FIGUR E 6. At r ia l f ibr i l la t ion wi th a rap id ven l I icu l~ response isseen in this EC G obtained in a middle-aged female patient withdyspnea after prolong ed bed rest. V /Q scanning was high p roba-b i l i ty for PE. She had no past history of atrial fibrillation.

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FIG UR E 7. Right bundle branch block, signified by an rSRpattern in lead V1 in the setting of a widened QRS complex, in apatient with documented PE. Also note the likely right ventricularhypertrophy (RVH) pattern, large R' wave in lead V1 and large Swaves in the mid to left precordial leads. Lastly, the chronicpulmonary disease pattern is suggested in this particular patient,RVH and low voltage in the limb leads.

a ted with PE, l ikely resul t ing from right a t r ia l hypert rophyor enlargement associa ted with acute obs t ruct ion from clot .P -pulmona le has been repor t ed in 2 to 30 of PE pa -t ients . ~s,19 Figure 9 shows the d evelo pme nt of P -pulm onalein a pa ti en t w ith PE --F ig 9A was ob ta ined on presen tat ionto the ED with s inus tachycardia and nonspecif ic ST seg-ment /T wave changes ; Fig 9B, obtained 6 hours la ter , re-vea led the deve lopmen t of P -pulmona le .

The c l a s s i c S IQ3T3 pa t t e rn , mis t akenly cons ide red pa -thognomonic for acute PE by many cl inic ians , i s seen lessf reque nt ly- -15 to 25 of pa t ien t s u l t ima te ly d i agnosedwith PE wil l have this pat tern. 4 A m ore com prehe nsiveevaluat ion of the PE pat ient and the character is t ics of pre-sentation reveal that this classic pattern is, in fact, quite rare.The UPET revea l s tha t approxima te ly 12 of pa t ien t s w i thangiographical ly documented acute PE ini t ia l ly had theelect rocardiographic S1Q3T3. 2o This pat tern (Figs 4 and 5)is character ized by an S wa ve in lead I , a Q wave in lead III ,and shal low T wa ve invers ions in one or more of the infer iorleads . In addi tion, the ST seg ments m ay be s l ight ly e levatedin the infer ior leads. A l though this f inding is cons is tent wi thright-s ided cardiac chang es , i t remains unclear i f this f indingactual ly predicts PE. Reports yie ld confl ic t ing data regard-ing i ts usefulness ; many authori t ies cons ider this abnormal-

FIGUR E 8. Another examp le of RBBB, RVH, and the chronicpulmonary disease pattern in a patient with PE.

FIG UR E 9. (A) Sinus tachycardia with nonspecific changes in apatient with dyspnea, plueritic chest pain, and hypoxemia. Subse-quent evaluation revealed PE . (B) Afte r admission to a critical careunit, P-pulmonale was noted in this tracing with large P waves inlead II.

i ty s t rongly sugges t ive when, in fact , i t shows a very poorsens i t iv i ty - -approx ima te ly 50 for the d i agnosi s o fPE. 1.8.16 Con sider the ex am ple in case 6 (Fig 5) in which theS1Q3T3 pat tern was noted in a pat ient who did not have PE.This e lect rocardiographic f inding should not be used as thesole cr i ter ion, ie , those pat ients lacking the appropria tesymptomology , for in i t i a t ing an eva lua t ion for pu lmonaryembol ism. The S1Q3T3 pat tern is usual ly short - l ived, re-solvin g within 2 we eks after PE. 15

Other S wave abnormal i t ies , that i s , separate from theclass ic S1Q3T3 presentat ion, are encountered frequent ly. Swave in lead I greater than 1.5 mm (Fig 10) and/or an Rwave-S wave ra t io greater than 1 in leads I and aVI wasnoted in 73 of pat ients diagnosed with PE. 21 A mo resubt le f inding is a s lurred S wave in leads V1 and/or V2.

The ST segment may be e i ther depressed (Fig 11) orelevated (Fig 12) in the PE pat ient . Minimal ST segmentdepress ion is a common f inding on the ECG in such pa-t i en t s . More pronounced depres s ion may a l so be encoun-tered in the anterior, inferior, and lateral distributions (Fig11); in this case , the ST segment depress ion l ikely repre-sents myocardial i schemia resul t ing from the physiologics t ra in of the PE i tse l f . Less marked ST segment e levat ion,less than 1 mm , is a lso frequent ly seen. The S1Q3T 3 p at ternma y be associa ted with ST se gmen t e levat ion in the infer iorl eads . The RBBB pa t t e rn may presen t w i th ST segmentelevat ion in the r ight precordial leads ( leads V1 and V2).

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. . . . . . . . . . . . . . . . . . . . . . . ~ T P~ ELI~ I~ ~ r~ I ~ ~ v ~ .~VR vl ~4

. ~ ) ~ L j ~ . ~ . ~ ~ 4

FIG UR E 10. A large S wave in lead I is seen in a PE patient.

S ign i f i can t S T segm ent e leva t ion cons i s ten t wi th acu temyocardia l infarc t ion is qui te rare .

The p resence o f an te r io r subep ica rd ia l i s chem ia causedby PE manifes ts as inverted T waves (F igs 2 and 12) in thef igh t to m id p record ia l l eads ( l eads V1 to V3 . 8,16 Ear lys tudies a t t r ibuted this pat tern to coronary insuffic iency.More recen t s tud ie s , however , sugges t e i the r ca the -cho lam ine - o r h i s t am ine - induced i s chem ia . 8 Di f fuse T waveinve rs ion ra re ly i s d iagnos t i c fo r P E .

The c l in ic ian m us t v iew the ECG as a whole in theeva lua t ion in the pa t ien t wi th p re sum ed P E ; com bina t ions o fva r ious e lec t roca rd iograph ic abnorm a l i t i e s and the i r d iag-nos t i c va lue have been cons ide red . S inus t achyca rd ia andnonspec i f i c S T segm ent /T wave changes a re f requen t ,though nonspec i f i c , f ind ings in the P E pa t i en t ; when no tedtogether, these f indings represent the most frequently en-counte red e lec t roca rd iograph ic pa t t e rn in the P E pa t i en t anda re no ted in approx im a te ly 50 o f cases a t som e po in t inthe i r course . Unfor tuna te ly , these f ind ings , though com -m on ly s een in the P E pa t ien t , a re ex t rem e ly no nspec i f i c andin no way ind ica t ive o f pu lm o nary em bolus . 6,9 Unles s thec l in ica l p re sen tat ion , i e , the ch ie f com pla in t and /or phys ica lexam ina t ion sugges t s P E , the phys ic ian wi l l l ike ly m iss thed iagnos i s i f he o r she re li e s on the E CG as the so le s c reen-ing tool .

E lec t roca rd iograph ic pa t t e rns ind ica t ive o f acu te r igh tven t r i cu la r s t ra in a re no ted f requen t ly on the E CG of the P Epatient . I n one large s tu dy 15 of pat ients with d ocu men tedP E , 82 o f cases had e lec t roca rd iograph ic changes sug-ges t ive o f acute f ight ventricular s t rain. These f inding sinc luded :

i ~ J [

FIGU RE 11. Sinus tachycardia and ST segment depression inleads V2 to V6 in a PE patient.

F N

i J I ~ ~

FIG UR E 12. ST segment elevation in leads V2 to V5 is seen ina PE patient. Addi tional ly, T wave inversions are also seen in thisdistribution.

Incom p le te r igh t bundle b ranch b lock ; S 1Q3T3 pa t t e rn ; Q wave in lead III ; Inve r ted T waves in l eads I I I , V2 and V3; and /or Inc rease in the fron ta l QRS ax i s o f > 20 degre es? 5Anoth e r g roup of inves t iga to rs l ead by S ree ram 14 sug-

ges ted tha t P E should be cons ide red whe n 3 o r m ore o f thefo l lowing e lec t roca rd iograph ic changes a re encounte red :

I n c o m p l e t e or c o m p l e t e R B B B ; La rge S waves in l eads I and a VL; A shif t in the t rans i t ion zo ne in the precordia l leads to

V5; Q waves in leads I I I and aVF (no t l ead I I) ; Right -ax i s dev ia t ion ; A low vo l tage QRS com p lex in l im b leads ; and /or T w ave in vers ion in inferior a nd anterior leads . 14F igure 13 i s an exam ple o f an EC G obta ined f r om a

pa t i en t wi th acu te P E . Num erous f ind ings a s sugges ted byS ree ram e t a114 a re no ted , inc lud ing incom ple te RBB B, f igh tax i s dev ia t ion ( - -12 0 degrees ) , l a rge S wav es in l eads I andaVI, and T wave invers ions in the anterior and inferiorleads . P etruzzel i and col lea gues -~1 s tudied 21 e lectrocar dio-graph ic abnorm a l i t i e s in 245 pa t i en t s wi th suspec ted P E--60 of pa t i en ts u l t im a te ly had P E. Those pa t ien t s d iag-nosed wi th P E were found to m ani fe s t the fo l lowingp a t t e r n s m o r e c o m m o n l y :

P R segm ent d i sp lacem ent ; De laye d R wave ( l ead aVr); S lu r red S wave ( l eads V1 or V2) ; S 1Q3 T3 pa tt e rn ; T wave inve rs ion ( l eads V1 or V2) ; and /or Diffu se T wa ve invers ions . ~

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FIGURE 13. Numerous indings as suggested by Sreeram et a114consistent with PE are noted, including incomplete RBBB, rightaxis deviation (--120 degrees), large S waves in leads I and aVI,and T wave inversions in the anterior and inferior leads. In additionto the Sreeram et a114 criteria, RVH (prominent R' wave in lead V1with right axis deviation) with strain (ST segmentFl wavechanges) is noted.

Alternatively, Nazeyrolas et al studied 70 patients admit-ted for suspected PE and found only an S wave in lead I andQ wave in lead III significantly more c ommon among thosewith confirmed PE. 12 Rodger et aP 9 studied the ECGs of246 patients with suspected PE (49 with PE) comparing thefrequency of 28 different electrocardiographic findings sup-posedly associated with the diagnosis. Of these, the inves-tigators found only sinus tachycardia and incomplete RBBBsignificantly more common in PE patients. In this studypopulation, Sreeram's gui do 4 of 3 or more findings on theECG had only a 26.7% sensitivity and 57.1% positivepredictive value for PE. Moreover, the S 1Q3T3 pattern wasequally prevalent among those with and without PE. 19

ON LUSIONPE is a very elusive disease process lacking conclusiveclinical findings to aid in the diagnosis. The true goldstandard is pulmonary angiography. However, this cannotbe done on every patient that presents with a concerningstory. As an independent marker, the ECG continues to bea limited study because of its poor sensitivity. The transientnature of electrocardiographic abnormalities and the oftennonspecific changes reduce the effectiveness of the test as asingle agent. Serial ECGs do not improve the ability todiagnose PE. 14 Lastly, cornorbid states and their associatedelectrocardiographic patterns further confound the pictureprovided by the ECG. The electrocardiographic abnormal-ities described earlier coupled with the appropriate clinicalpicture, however, can be helpful in the decision to pursuePE as a diagnosis.

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