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ID naloge: 95 Letnik: 2000 Predmet: interna medicina
Motnje srcnega ritma pri testu z nagibno mizo in nitroglicerinom
Avtor: Melita T. Kermavnar
Mentor: prof. dr. sci. Anton Grad, dr. med., asist. mag. Bernard Meglic, dr. med.
Uvod. Sinkopa je prehodna izguba zavesti in posturalnega tonusa, ki nastane zaradi nenadnega zmanjšanja krvnega pretoka skozi možgane. Najpogostejša oblika je nevrokardiogena ali vazovagalna sinkopa, pri kateri pride do zmanjšanja krvnega tlaka in upocasnjenja srcnega utripa. V preteklosti je bila vecina nevrokardiogenih sinkop uvršcena med sinkope neznanega vzroka zaradi težav pri ugotavljanju vzrokov sinkope. V sodobni diagnostiki za potrditev nevrokardiogene sinkope uporabljamo test z nagibno mizo; tako lahko 50 - 60 % sinkop prej neznanega vzroka uvrstimo med nevrokardiogene. Test z nagibno mizo je zanesljiv in neinvaziven postopek, katerega obcutljivost lahko povecamo z uporabo nitroglicerina. Z vecjim številom pozitivnih odzivov na testu, pricakujemo tudi vec motenj srcnega ritma v obliki prezgodnjih utripov ali celo asistolije, tako se postavlja vprašanje, ali predstavlja test z nagibno mizo in nitroglicerinom vecjo nevarnost za preiskovanca kot test brez uporabe nitroglicerina.
Preiskovanci in metode. Primerjali smo skupino 565 preiskovancev, pri katerih je bil opravljen test z nagibno mizo brez nitroglicerina (skupina A), in 546 preiskovancev, ki so v 30. minuti testa dobili nitroglicerin pod jezik (skupina B). Uporabili smo protokol testa, ki ga je opisal Fitzpatrick s sod. Po 10 minutah v ležecem položaju, dvignemo bolnika na nagibni mizi na kot 60o, sledi 45 minut testa. Preiskovanci v skupini B so v 30. minuti dobili nitroglicerin (AngisedN) pod jezik. Med testom smo kontinuirano snemali enokanalni EKG s površinskimi elektrodami, posnetek je bil preko monitorja zapisan na trdi disk osebnega racunalnika. Na EKG posnetku smo analizirali motnje srcnega ritma in jih razdelili v podskupine glede na pogostost pojavljanja: pretežno pred dodatkom nitroglicerina, pretežno po dodatku nitroglicerina ali tokom celega testa. Izracunali smo specificnost in obcutljivost testa, ter cas do pojava sinkope. Rezultate smo statisticno ovrednotili s ?2 testom in Studentovim t-testom.
Rezultati. Pogostost motenj srcnega ritma je pri testu z nagibno mizo in nitroglicerinom vecja kot pri testu brez nitroglicerina (p < 0,02). Vec motenj se pojavlja pri ženskah (p < 0,005). Pri 51 preiskovancih so se motnje ritma pojavljale enako pogosto pred in po nitroglicerinu, pri 10 preiskovancih je bilo vec motenj ritma pred, pri 42 pa po nitroglicerinu. Zabeležili smo tudi 20 asistolij, od katerega jih je bilo 12 pri skupini B, vendar oživljanje pri nobenem bolniku ni bilo potrebno, saj se je srcna akcija v kratkem vzpostavila sama. Pri testu z nagibno mizo in nitroglicerinom smo dobili vec pozitivnih odzivov, z obcutljivostjo 63,2 %, v primerjavi s testom brez nitroglicerina, pri katerem je obcutljivost le 18,2 % (p < 0,0001). Specificnost testa se z uporabo nitroglicerina zmanjša (90,6 % vs. 50,6 %).
Zakljucek. Ugotovili smo, da je testiranje z nagibno mizo in nitroglicerinom, kljub vecjemu številu motenj srcnega ritma, zanesljiv in varen postopek za potrditev refleksne nevrokardiogene sinkope. Z vecjim številom pozitivnih odzivov na testu, izzovemo tudi vecje število motenj srcnega ritma, predvsem supraventrikularne in ventrikularne prezgodnje utripe, vendar le-te ne ogrožajo bolnika. Pri manjšem deležu bolnikov smo opazovali kratkotrajne asistolije, tako da oživljanje ni bilo potrebno pri nobenem bolniku, zato zakljucujemo, da je test z nagibno mizo in nitroglicerinom varen.
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[Abstract / English version]
Arrhythmias in head-up tilt table test
Author: Melita T. Kermavnar
Mentor: prof. dr. sci. Anton Grad, dr. med., asist. mag. Bernard Meglic, dr. med.
Introduction. Syncope is defined as a transient loss of consiousness and postural tone caused by sudden decrease of cerebral blood flow. The most frequent form is neurocardiogenic or vasovagal syncope, characterized by hypotension and bradycardia. In the past there have been a lot of difficulties diagnosing this form of transitient loss of consiousness. Until recently most of the neurocardiogenic syncope were classified as syncope of unknown origin, but with the use of head-up tilt table test (HUT) 50-60% of these syncope were proven to be neurocardiogenic in origin. HUT is a safe noninvasive test, which can be potentiated with sublingual nitroglycerine to obtain a larger positivity rate. With higher number of positive test results we also expect a larger number of arrhythmias in the form of extrasystole or even asystolia, but the question remains: is nitroglycerine provoked HUT potentionally more harmful for the patient.
Patients and methods. We compared a group of 565 patients (group A) who were tested with passive HUT to a group of 546 patients by whom HUT was potentiated with sublingual nitroglycerine. We used a HUT protocol, which was previously described by Fitzpatrick et al. First 10 minutes of supine position were followed by 45 minutes of passive tilt at 60°. Patients in group B were given 0,5 mg of nitroglycerine (Angised®) sublingually in the 30. minute of test. During the test we recorded a one-channel ECG with surface electrodes, and with mercury sfingomanometer blood pressure. On the ECG record we analysed arrhythmias that occurred during the test and subgrouped these arrhythmias acording to the time in which they appeared: predominantly before the administration of nitroglycerine, predominantly after the administration of the drug or indifferently through the whole test. We defined the specifity and sensitivity of HUT for both groups. Results were compared using the ?2-test and Student t-test.
Results. We observed more arrhythmias in group B (104 cases) including asystole. The results show that almost half of arrhythmias (51 cases) did not depend on administration of nitroglycerine. Of the other 53 cases 42 appeared predominantely after the administration of the drug and only 10 predominantely before nitroglycerine was used. We also observed 20 cases of asystole, 12 of which were in the group B, but heart action returned spontaneously and no resuscitation manouvers were needed. The sensitivity was higher in nitroglycerin potentiated HUT than in passive HUT (63% vs. 18,2 %, p < 0,0001).
Conclusion. We conclude, that nitroglycerine potentiated head-up tilt table testing is a safe method for diagnosing neurocardiogenic syncope. With a higher positivity rate more arrhythmias are provoked, especially supraventricular and ventricular extasystole, but they do not represent a threat to the patient. In the minor proportion of patients we observed short-lasting asystole, but no resuscitation maneuvers were needed, so we conclude that the nitroglycerine potentiated HUT is safe.
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