Sleep apnea and aortic dissection

A 62-year-old man presented with obstructive sleep apnea, congestive heart failure and Cheyne-Stokes respiration. Further evaluation revealed a chronic dissecting aneurysm of the aorta causing vena caval obstruction. Surgical correction or the aneurysm dramatically improved ventricular function with resolution of Cheyne-Stokes respiration. Nasal continuous positive airway pressure corrected the obstructive sleep apnea and associated clinical features. The cardiopulmonary interactions between sleep apnea and aortic dissection are discussed.


CASE PRESENTATION
History: A 62-year-old mal e presented with a long history of OSA and a recent hi story of congestive heart failure .He reported very loud, habitual snoring and excessive daytime sleep iness for 40 years.Initially.he had passi ve sleepiness but it became so severe that he had frequen t road traffic accidents and d iscontinued driv ing.Hi s wife had witnessed apneas during sleep tor 20 yea rs.T he patient had been obese all his life and.on presentation, weighed 153 kg wit h a body mass index of 46 kg/111 2 .He reported drinking 6 to 8 oz of alcohol per day for several years_ The patient had been treated for hypertens inn !'or IO years.(4).Period ic leg movement.were scored if they occurred independently of an arousal from sleep and were part o f a series or fo ur or more consec utive move ments las ti ng 0.5 to 5 .0s wit h an intermovement interval of 5 10 90 s (5 ).CSR was defined as peri odic breathing wit h centra l apnea or hypopnea al tern at ing with hyperpnea in a crescendo/descrescendo pattern.and the dura tion o r CSR 70 EEG),,.,.,...,.,,.~.N,,\J.i.µN ly...,.,r".~•/\___..,.,.,~,.--\~_,,..,,,,, EEG""'"-.;,,,~i,f.Jr,A-.'f.,"""'-.~~,..._,,,,.,..__.._,J..,.,._,,,~,,.,,..  The overn igh t sleep st udy revealed severe sl eep apnea.period ic leg movement s during s lee p and rap id atri a l fibri llation (Table I).During nonrapiJ eye movemen t (NREM ) sleep, there were features hoth o f OS J\ , man ifested by rib cage paradox , and CSR wit h a classic cresce ndo/decrescendo appearance (Figure l ).During rapiJ eye movemen t (REM ) sleep, apneas were clearly ob tructive without ev idence of CSR (Figure 2 ).Apneas were 30 to 40 s long during NREM sleep and up to 65 s long during the brief peri od o f REM sl ee p.They were assoc iated with se ve re hypoxcm ia a nd sl ee p d isruptio n.T ran scu taneous ?CO2 was low duri ng both wake fulness anJ sleep.The patie nt was im med iately p laced on nasa l continuous posit ive airway pressu re (CPAP ) and a repeat sleep study de monstrated that IO cmH20 nasal CPA P corrected up per ai rway obstruction anJ maintained satisfactory oxygen sat urat ion Juring sleep.Fu rthermore.once the uppe r airway was stabilized by na al PAP.CSR became more ap pare nt wi th a typica l crescendo/dec rescendo appearance (Figure 3).Th is occurreJ on ly duri ng NREM sleep and was assoc iated with mi Id oxygen desaturation to between 85 and 90 %.T he patie nt continued to have frequen t periodic leg movements during sleep and rapid atrial fibri llatio n.
Pulmonary function : Spirometry showed a vit al capacity of  T his was confi rmed hy radi onuc li de ang iography.which re-vealeJ a left ve ntricu lar eject ion frac tion of 16%.In aJJ ition, echocan.liographyrl' vea led that the ascending aorta was Jilated, and aortic d issection was suspected .
Radiology: Chest radi ography showed caruiomega ly and an anterior med iast inal mass (Figure 4).Furthe r eval uat ion by computeri zed tomography confirmed the presence o r a very large dissect in g ane urys m in the ascend ing aorta .
Operation: Surgical repair was recom mended since it was felt there was a sig nific1nt risk or ao rtic ru pture .Fol lowing a m idli ne sternotorny.a 12 u11 d issecting ane urysm of the asce nding aorta was rou nJ that was compress ing the vena cava and displac ing the heart infe riorly and lateral ly to the left.The su rgeon al so reported evide nce of old pericard itis .A Dacron tube graft replaced the abnormal aorta, and o nce the aneurysm was removed, the heart moved bac k to a normal position.Patho logica l exam inat ion (11' the resected aorta s ubsequent ly reve al ed a J o uble -barre l lumen w ith fibro intimal hyperplasia cons istent with chron ic metl ial wall dissection. Can  Progress: Postoperat ively.the pat ient diureseJ rapid ly anJ there was a ma rked reducti on in his faci al size.In re trospect.it was apparent that he had sign ifi cant superior vena caval obstruct ion.He reverted spontaneous ly to sinus rhythm.Resting rad ionucl ide ,mg iogra phy two weeks foll owing surgery revea led a le ft ventri cu lar ejection fractio n o r 549'1' w ith persistent left ventricu lar en large ment.He was discharged from hospita l 25 days fo ll owing his surgery on .:nalaprilI 0 mg Jaily, e nteric coated acetyl sa licyli c acid.anJ sa lt and ca lorie restriction.Congest ive heart fail ure hatl resolved and he did not req ui re d iure tic therapy.Over the ne xt year. he cont inued to use IO cmH 20 nasa l CP P during slee p.There was a dramatic improvement in his sleep qual ity and dayti me function w ith com plete reso lut ion or hypcrsomnolence.A lthough he re mained obese, hi s weight fe ll to 118 kg (body mass index 38.5 kg/m~l with a reduction in his nec k circum ference to 47 cm.Cl inical ly. he rrn1ained free o f heart fail ure althou gh atrial rib rill ation returned, requiring treatment with d igox in and amiodarone.which converted him to normal sinus rhy thm.He maintained norma l left ven tricul ar systol ic function although he had pers isten t impairment of lert ventricu lar diastoli c fun ct ion.whi ch was attribu ted to hype rtension anJ previo us caruiac hi story .Overnight pol ysomnography was repeated 13 mon ths fo llowing repai r o r his aortic ane urysm (Table I ).T he study was pe1formed on and off nasal CPAP.Off nasal CPAP, he conti nueJ to have signific.1ntOSA with assoc iated hypoxemi a anJ sleep d isru ption.Howe ver, there was no ev idence o f CSR a nd tC02 wa, clevateJ compared with the relat ive hypocapn ia he experienced duri ng the fi rst sleep stud y .During the second part of the st udy.his OSA was con-ected by 10 cmH20 nasa l CPAP.The pat ient re mains well three years fo llowing his init ial presenta tion.

DISCUSSION
The patien t described he re had cl iniL•,d and polysonmogra phi c e vide nce of both OSA and CSR .The long h istory o r lou d snoring, witnessed apneas and excess i v1.: dayti me sleepiness are cons isten t wi th OSA. and the recent his tory o f congestive heart failure pred ispo sed the patient to de velop CSR.Al thoug h in termittent parado xical breath ing was p resent throughou t the s leep study.obstruc ti ve ap ne a was most obviou s duri ng REM s leep (Fig ure 2 ). the sleep stage du rin g which upper airway occl usio n is most likely to occur.CSR was only seen during stage I and 2 NREM s leep (Figure I) and became more o bvio us once the uppe r airway was stabilized by nasa l CPAP (Fig ure 3).The pathogenesis of CSR is cl ose ly re lated to destabil izatio n of" the metabolic control system.which is the prima ry reg ulator or venti lat ion during NREM sleep (6) .Hence. the rel ati o nshi p between sl eep stage and s leep-disordered breathing in o ur pati e nt is cons istent with the current understa nd ing o f the pathogenes is o r these two d ifferen t fo rms o f s lee p apnca.
T he uni que feature of this case is the pote nt ial interactio n between sleep apnea and aortic d issec tio n and the ro le they may have played in e ach others • pathogenesis.It has be n proposed by m1r c ardiovasc ubr colleagues that the pat ie nt•s aortic di ssect ion started during the e pisode of acute pericarditis seven years prev ious ly .In addition.he was hy perte nsive.whi c h is a know n ri , k fac tor for the deve lopment o f aort ic di ssection.Howeve r, th e re was also clinical a nd po lyso mnogra phic ev idence of OSA whic h.hi storica ll y. had been presen t for 40 years.Obstructive apnea is associated with large negative intratho rac ic pressure sw ings due to force d inspirati on against an occluded upper airway (7).Each apnea generates a subst ant ial pressure g rad ie nt across the le ft ventricle and aort ic w all.Obstruc ti ve apneas are also kno wn to cause acut e elevatio n o f system ic blood pressure d uring sleep (8 ).It is possib le that this repetitive incre ase in the pressure grad ient across the aortic wall and the inte rmi tt ent rise in systemic bl ood pressure over many years may have e xtended the aortic dissec ti o n that commenced duri ng the e pisode of acute pericard iti s .
In addi ti o n to OSA. the patiL'.11! al so had polysomnograph ic ev idence llf CSR (Fi g ures l and 3 ).Si nce the pat ie nt also had congcsti ve heart fa il ure. it is reasonable to assume that his CSR was caused by le ft ve ntric ular dysfunction.T he re were many risk facto rs fo r the deve lopment of le rt ve ntri cular dysfunction in this patient includi ng hypertension.obesity.alcohol co nsum pt io n and prev iou s perica rdi tis (l)).In additi on, OS A may have exacerbated pre-ex isting left \ entric ubr dysfunction Ol although it is un like ly to have caused it de novu ( 10).Ho wever.we beli eve that the most significa nt GtUSL' of impa ired left ve ntric ular functi o n was ve na ca val obstruction caused by a large d issecting aneurysm of the ascending aorta.It is likely that venous ret urn was cri tically red uced not only by com pression o f the vcna cava but also by di sp lacement o f the heart.T his was supported hy the in trao perati w findi ngs, clinical features o f su pe ri o r vcna ca val obstruct ion and the rapid cliniL•al and echocardi ographic improvement fo l lowing surgery.The pal ien t • s con t i 11ued improvemen t and the abse n e of CSR three YL'ars fol low ing surge ry furt he r support these suggest ions.

CONCLUSIONS
We re port a pati en t wi th L'Oex ist ing dissec ting aneurys m uf the aorta and sleep apnea.We bel ie ve that vc na caval obstruc tio n assoc iated with the a neury sm c aused CSR d uring sleep.Furthermo re , we specul ate th at long-stand ing OSA may have cont ributed to the deve lop ment of aortic di ssec tion.

TABLE 1
Overnight polysomnography at presentation and 13 months following surgery, on and off nasal CPAP SWS Slow wave sleep; tC(k (TST) Mean transcutaneous PC(k in mmHg during TST; TST Total sleep timeSeven years prev ious ly. he developed viral pericardit is and ~1 sma ll pericardia!effusion.which was detected by echocardiography.This was compl icated hy atrial fibrillation , which was successfully cardioverted.O ver the past few months.hedcve loped increasi ng shortness of breath and peripheral edema.His medications included furosem iJe, digox in.amiloride, ena la pri l and all opurinol.Physical examination: T he patient was a morb idl y obese male .He had atria l fibrillat ion wit h a ventri cul ar response of 150 beats/ min .Blood pressure was 140/80 mmH g.Neck circ umference was 51 cm and he had a large uvu la and crowded oropharynx .Cardi ovascula r ex am inati on revealed an e levated j ugular venous pressure.disp laced le ft