British Heart Journal, 1970, 32, 99.

Comparison of left atrial pressure andwedge pulmonary capillary pressurePressure gradients between left atrium andleft ventricle

David Verel and Norman H. StentifordFrom The Cardio-Thoracic Unit, Northern General Hospital, Sheffield

Simultaneous records of wedged pulmonary capillary pressure and left atrial pressure have beenmade in I2 patients. The pressure changes in the left atrium preceded those in the pulmonarycapillary bed by o-o6 to O0I4 sec.

This delay, together with the damping of the wedged pulmonary capillary pressure, may resultin a false appearance of an end-diastolic gradient between the left atrium and the left ventricleif simultaneous wedged pulmonary capillary pressure and left ventricular tracings are compared.

In severe aortic valve incompetence thereflux of blood into the left ventricle from theaorta during ventricular diastole may be soprofuse that the pressures in the left ventricleand aorta equalize before the end of diastole.In these circumstances the end-diastolicventricular pressure may exceed the leftatrial pressure, so that the mitral valve isprematurely closed by the rise in ventricularpressure (Wright, Toscano-Barboza, andBrandenburg, I956; Colvez et al., I959).In some cases this premature closure is pre-ceded by regurgitation of blood into the leftatrium shown by left ventricular angiocardio-graphy. This phenomenon is likely to accountfor some, if not all, cases of Austin Flintmurmur (Wigle and Labrosse, I965; Lochaya,Igarashi, and Shaffer, I967).Premature mitral valve closure may also

be seen in lesser degrees of aortic incom-petence where the aortic and ventricularend-diastolic pressures have not equalized,either as a result of a change in the atrio-ventricular rhythm (Colvez et al., I959), orbecause the end-diastolic pressure, while notreaching aortic diastolic levels, exceeds theatrial pressure (Wigle and Labrosse, I965).A similar phenomenon has been shown indogs (Welch, Braunwald, and Sarnoff, I957).Since the occurrence of premature mitralvalve closure may be regarded as evidenceof a significant milestone in the decline ofReceived 3 June I969.

left heart function in aortic incompetence,measurements of left atrial and ventricularpressure are of considerable importance.Most of the studies discussed above were

made by direct pressure measurements fromthe left atrium, left ventricle, and aorta. Inman, this involves a difficult catheterizationtechnique in patients whose clinical conditionmay be poor. The recording of wedged pul-monary capillary pressure provides a muchsafer way of assessing the left atrial pressure,and, indirectly, the ventricular end-diastolicgradient. Both Oliver, Gazetopoulos, andDeuchar (I967) and Lochaya et al. (I967)have shown reversed gradients across themitral valve by this technique in patientswith aortic regurgitation.

Transseptal left atrial catheterization hasbeen in routine use in this unit for mitraland aortic valve assessment for several years(Verel and Taylor, I967). The prospect ofusing the less risky wedge pressure measure-ments prompted a comparison of the tech-niques using simultaneous measurements ofwedged pulmonary capillary pressure andleft atrial pressure.

Subjects and methodsThe results obtained in I2 patients are reportedin this paper. In Cases I-4 the valve lesions wereconfined to the mitral valve. Cases 5 and 6 hadmitral and aortic valve lesions. The remaining6 patients had pure aortic valve incompetence.

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Patients were catheterized under light sedationwith I50 mg. amylobarbitone. Retrograde aorto-graphy was performed by the Seldinger tech-nique using PE 240 catheters, 125 cm. long. Theleft atrium was catheterized by the method ofAldridge (I964) in most cases or, in a few, by amodification of the Ross technique (Verel, I967).Introduction in all cases was by Seldinger wire.Wedged pulmonary capillary pressure measure-ments were made by a I25 cm. 7F Cournandcatheter introduced through an antecubital veinincision. The Brockenbrough catheter (U.S.C.I.)used for the left atrial pressure measurements wasconnected to the pressure transducer by a lengthof recording tubing, making a total catheter lengthof I25 cm.

Pressure was recorded on a Cambridge photo-graphic recorder using Cambridge InstrumentCompany transducers and amplifiers. In allrecordings the same pressure range was used foreach transducer, zero being checked before andafter each recording. The calibration of eachtransducer was checked against a mercury mano-

meter. All recordings were made without elec-tronic or mechanical damping.

LAP WPCP &

-K)rXf-A AAA t- 1555~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

FIG. I Simultaneous recording of left atrialpressure by transseptal catheter and wedgedpulmonary capillary pressure by Cournandcatheter. The wedged pulmonary capillarypressure closely resembles the left atrialpressure, but is delayed and slightly damped.

TABLE Results of catheterization in 12 patients

Pressures (mm. Hg)

Case Age Diagnosis Rt. Rt. Pulm. Wedged Lt. Lt. Aorta End-diast. Time RhythmNo. (yr.) atrium ventricle artery pulm. atrium ventricle gradient* lagt

capillary (sec.)I 34 Mitral stenosis 5/-2 30/0 30/I5 2I/15 22/12 I00/0 100/55 o-o6 Sinus

and incompetence rhythm2 40 Mitral stenosis 8/3 5015 50/30 i8/io 22/6 I50/I0 I50/80 - o-o6 Sinus

and incompetence rhythm3 49 Mitral stenosis 7/3 30/3 30/15 15/10 38/17 I00/6 ioo/6o - -14 Mitral

fibril-lation

4 48 Mitral stenosis I2/5 50/5 50/30 25/15 50/20 120/0 120/80 -012 Atrialfibril-lation

5 51 Aortic and mitral 6/-2 23/0 23/5 15/12 20/7 i6o/o i6o/8o O-I2 Sinusincompetence+ rhythmmitral stenosis

6 41 Aortic incom- 7/2 45/0 45/25 20/12 25/10 120/5 I00/50 3 OI4 Atrialpetence (aortic fibril-stenosis) (mitral lationincompetence)

7 33 Aortic 8/o 25/0 25/10 I2/5 20/5 120/5 120/30 8 012 Sinusincompetence rhythm

8 45 Aortic I0/3 20/3 20/I0 I5/Io I5/7 120/0 120/80 5 012 Sinusincompetence rhythm

9 59 Aortic I5/Io 8o/io 80/40 60/30 60/20 I60/20 I60/60 5 0-14 Sinusincompetence rhythm

10 42 Aortic 5/0 20/0 20/I0 I8/8 i8/8 II0/20 I60/40 6 0-14 Sinusincompetence rhythmII 46 Aortic 9/0 25/0 25/10 12/5 I5/5 120/5 120/45 3 0-14 Sinusincompetence rhythm

12 34 Aortic 7/0 20/0 20/8 7/5 Ic/5 II5/0 iI5/8o 0 o-o8 Sinusincompetence rhythm

* End-diastolic gradient is measured between the left ventricular pressure and wedged pulmonary capillary pres-sure (as shown in Fig. 2 and 3).t Time lag is delay in seconds between events recorded in left atrial pressure and the wedged pulmonary capillarypressure tracings.

Wid

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Comparison of direct and indirect left atrial pressures IO0

The recording system was tested at each cathe-terization to confirm that there was no significantdifference in the speed with which pressurechanges were transmitted through the catheters.On most occasions this was done by recordingpressure from the right ventricle simultaneouslyby the Cournand and Brockenbrough catheters,and from the left ventricle by the Brockenbroughand aortographic catheters. When this was notpossible, the transmission time was measuredfrom the R wave of the electrocardiogram on ahigh speed recording of ventricle pressure. Inmost cases there was no measurable differencein the timing of the recordings as the photographictraces merged. In no case was the difference intiming as large as 0o04 sec.

ResultsThe results obtained are shown in the Table.

In every case a simultaneous measurementof left atrial pressure and wedged pulmonarycapillary pressure was obtained. The systolicand diastolic pressures corresponded closelyin most cases. Where differences occurred theywere consistently due to damping of thewedged pulmonary capillary pressure traceleading to a lower systolic pressure, higherdiastolic pressure, or both (Luchsinger,Seipp, and Patel, I962). The largest errorswere encountered in 2 patients with puremitral stenosis (Cases 3 and 4, see the Table).

In all cases the wedged pulmonary capil-lary pressure trace lagged behind the record-ing of left atrial pressure by an interval whichranged from o.o6 to O'I4 sec. (Fig. i and theTable). This delay in transmission presumablyrepresents the time taken for the pressurewave generated in the left atrium to passthrough the pulmonary veins and capillarybed. The variability in this time lag is un-

explained. It is not related to the level ofpressure recorded, nor to the age or size ofthe patient. It is possibly significant that theshortest transmission times of o-o6 sec. werefound in 2 patients suffering from mitralincompetence without aortic valve disease(Cases i and 2) but a time of o-o8 sec. wasfound in Case I2 who suffered from pure

aortic incompetence.The simultaneous recordings of left ventri-

cular pressure and wedged pulmonary capil-lary pressure in the group of patients withoutmitral stenosis revealed an end-diastolicgradient in 6 patients (Cases 6-i i, Fig. 2

and 3). All were suffering from aortic in-competence of moderate to severe degree.One patient (Case 9) was in severe right andleft ventricular failure at the time of catheter-ization, remaining in this state with littlechange until successful operation relievedthe situation. In one other patient (Case I2)

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WPCP (Cournand) __.--O0F I G. 2 Simultaneous tracing of the leftventricular pressure and wedged pulmonarycapillary pressure. The record shows an

end-diastolic gradient of about 5 mm. Hgbetween the left atrium and left ventricle(Case ii).

with a mild aortic valve leak the transmissiontime was short (o-o8 sec.), and in this case

left ventricular pressure and wedged pul-monary capillary pressure tracings revealedno gradient (Fig. 4).The direct left atrial pressure tracings were

then compared with the left ventricularrecords. In Cases 6-i i the end-diastolicpressure in the left atrium was found to equalor exceed the end-diastolic ventricular pres-

sure in every case (Fig. 5). The gradientshown by the wedged pulmonary capillarypressure measurement was thus shown to be

FIG. 3 Simultaneous tracing of the leftventricular pressure and wedged pulmonarycapillary pressure from a patient in heartfailure. An end-diastolic gradient of 3-5mm. Hg is shown (Case 9).

tLV{Brockenbrouqhh- mm.Hq

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WPCP {Cournand)

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an artefact due to the time taken for thepulse wave to pass from the left atrium tothe pulmonary capillaries.

DiscussionThe delay between the events occurring inthe left atrium and the corresponding pres-sure changes recorded in the pulmonarywedge position is of considerable importance.When related to the happenings in the leftventricle it may be long enough to producean apparent end-diastolic gradient. In ourcases this gradient was due primarily todisplacement of the 'a' wave from the endof ventricular diastole to the beginning ofventricular systole. As a result, the recordedventricular end-diastolic pressure corres-ponded to the phase of atrial pressure pre-ceding ventricular systole. In addition, thereduction in the height of the 'a' wave onthe wedged pulmonary capillary pressuretracing in some cases increased the apparentleft atrial-left ventricular gradient. The delayin transmission along the pulmonary veinswhich was recorded in these patients rangedfrom o-o6 to O014 sec. None was a normalsubject, but it is likely that the normal delaylies in the range of o I2 to OI4 sec. as mostof the patients with pure aortic incompetenceand normal left atrial function had trans-mission times of this order. There may bemore than one factor responsible for theshorter times found in three patients (CasesI, 2, and I2). Two had considerable mitralincompetence without aortic valve disease.In these cases the reflux of blood from theatrium into the pulmonary veins may haveshortened the transmission time.

ReferencesAldridge, H. E. (I964). Transseptal left heart catheter-

ization without needle puncture of the interatrialseptum. American Journal of Cardiology, 13, 239.

Colvez, P., Alhomme, P., Samson, M., and Guedon,J. (I959). La pression de remplissage du ven-tricule gauche dans les grandes insuffisancesaortiques. Ses relations avec l'allongement de laconduction auriculo-ventriculaire. Archives desMaladies du Coeur et des Vaisseaux, 52, 1369.

Lochaya, S., Igarashi, M., and Shaffer, A. B. (1967).Late diastolic mitral regurgitation secondary toaortic regurgitation: its relationship to the AustinFlint murmur. American Heart Journal, 74, I6I.

Luchsinger, P. C., Seipp, H. W., Jr., and Patel, D. J.(I962). Relationship of pulmonary artery-wedgepressure to left atrial pressure in man. CirculationResearch, II, 315.

Oliver, G. C., Jr., Gazetopoulos, N., and Deuchar,D. C. (I967). Reversed mitral diastolic gradient inaortic incompetence. British Heart J'ournal, 29,239.

Verel, D. (X967). Catheterization of the left atrium byRoss needle and Seldinger wire techniques. BritishHeart Journal, 29, 380.

-- '.(PE 240)-r----0 ---t---

WPCP iId)_ j-0f-1.~~~~~~~~~~~~~~~~~~~- ...o_

FIG. 4 Simultaneous left ventricular andwedged pulmonary capillary pressure tracingshowing no end-diastolic gradient (Case 12).

-, and Taylor, D. G. (1967). Assessment of aorticvalve stenosis by left ventricular puncture and leftatrial catheterization. In Proceedings of the BritishCardiac Society. British Heart3journal, 29, 633.

Welch, G. H., Jr., Braunwald, E., and Sarnoff, S. J.(I957). Hemodynamic effects of quantitativelyvaried experimental aortic regurgitation. Circula-tion Research, 5, 546.

Wigle, E. D., and Labrosse, C. J. (I965). Suddensevere aortic insufficiency. Circulation, 32, 708.

Wright, J. L., Toscano-Barboza, E., and Brandenburg,R. 0. (1956). Left ventricular and aortic pressurepulses in aortic valvular disease. Proceedings of theStaff Meetings of the Mayo Clinic, 31, 120.

FIG. 5 Simultaneous left ventricular andleft atrial pressure tracing from Case II.The end-diastolic gradient seen in Fig. 2is an artefact due to the displacement anddamping of the left atrial pressure in thewedged pulmonary capillary pressure record. on A

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