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2017-04-29  Complete heart block  © Islam Badr  www.TheFetus.net

Complete heart block
Islam Badr, M.Sc.*; Rasha Kamel, MD*, Heba Ahmed Elzayat, M.Sc. *; Reem Mohamed Aboelela, M.Sc. **, Fath Allah Fathy Awad,MD***; Sameh Abdel Latif Abdel Salam, MD****
 
* Fetal medicine unit, Cairo University, Egypt;
** Om El Masryeen Hospital; Cairo, Egypt;
*** Imbaba Hospital, Cairo, Egypt;
**** Radiology department, Kasr Alainy hospitals, Cairo University, Egypt;


Complete heart block is the end result of a destructive process that affects the cardiac conductive tissue and leads to atrio-ventricular dissociation that results in bradycardia and may end in heart failure 1. A link to an immune mediated destructive process involving trans-placental passage of anti-Ro/SSA and/or anti-La/SSB that damage the fetal myocardiocytes is now well established 1. Structural heart disease should be ruled out in fetuses of complete heart block since it accompanies a significant proportion (about 50%) of these fetuses specifically left isomerism and discordant atrio-ventricular connections 1, 2. In one study, Lopes et al. retrospectively reviewed 116 cases of complete heart block diagnosed in their institution over 18 years. They identified the association with structural heart disease, ascites, atrial rate below or equal to 120 and ventricular escape rate below 55 as risk factors for mortality2. The presence of structural heart disease is an ultimately poor prognostic sign and in particular left isomerism 2, 3. Management strategies vary significantly between one center to the other with highly controversial data present in the literature about the efficacy of corticosteroids, beta stimulation and other medications taking into consideration their adverse fetal and maternal effects 1, 3. The role of maternal steroids may be more beneficial for resolution of fetal hydrops if occurred in cases of complete heart block1,3. This controversy extends to the prophylactic approaches with IV immunoglobulin and hydroxychloroquine most commonly used for that purpose1

 
Case report

A 24-year old PG woman presented to Cairo University Fetal Medicine Unit at the 32 week of gestation because of persistent bradycardia noted both by fetal heart auscultation and an ultrasound study performed during her antenatal care. Our ultrasound examination revealed the following:

- Cardiomegaly with thick, hypertrophied ventricular free walls.
- Severe tricuspid and mitral regurgitation.
- Structurally normal heart with normal veno-atrial connections and concordant atrio-venticular and ventriculo-arterial connections.
- Persistent regular bradycardia.
- Complete dissociation between atrial and ventricular contractions.
- Ventricular escape rhythm 48 bpm that declined to 42 bpm at the 35th week of gestation.
- Regular atrial rate of 120 bpm that declined to 100 bpm at the 35th week of gestation.
- Some of the atrial contractions were synchronous with the ventricular contractions and thus taller than the usual A waves (cannon A waves).
- Slow ventricular rate discordant from the higher atrial rate made the ventricles accommodate more blood volume than in normal heart rhythm conditions. This eventually led to two results. The first one is represented by the vigorous systolic arterial distension of both ascending aorta (and its arch) and main pulmonary artery (and its arterial duct) attributed to much higher blood volume ejected during ventricular systole. The second one is related to elevated ventricular filling pressures causing absence of early diastolic filling (E wave) prior to ventricular contractions that were accidentally preceded by atrial contraction. The elevated ventricular filling pressures were also attributed to cardiomyopathy with consequent papillary muscle dysfunction and poor leaflet cooptation of AV valves (manifested by severe MR and TR). 
 

Complete heart block was diagnosed based upon our ultrasonic findings. A laboratory work-up has been performed and revealed that the mother is seropositive for both anti-Ro/SSA and anti-La/SSB with very high titers with the CBC also revealing low platelet count at 40,000 thousands/cm2. The mother was sent to a connective tissue disease specialist who recommended immediate initialization of steroids for the sake of normalization of platelet count before delivery. The high-risk pregnancy team added salbutamol for the sake of increasing the ventricular rate but the ventricular escape rhythm did not increase at all. The timing of termination of pregnancy was controversial but they decided to continue until the 37th week of gestation for the sake of maturity against other recommendations of maternal stabilization followed by immediate delivery in the shadow of the fetal heart failure status which might makes the termination and pacing outside the uterus more preferable. The fetus was delivered after the completed 37th week of gestation and stayed 4 days in the incubator. Neonatal death occurred before any attempt of pacing. 


In all images the white arrows point to the ventricular contractions and the red arrows point to the atrial contractions.
 

Video 1
: four-chamber view of the fetal heart demonstrate the very slow heart rate. Note also the cardiomegaly and the thick, hypertrophied ventricular free walls. The four-chamber view is structurally unremarkable.




Images 1 and 2: M-mode tracing of both the right atrium and the left ventricle obtained with different sweep speeds. Note the regular atrial contractions at a rate of approximately 102 bpm and the regular ventricular contractions at a much slower rate (around 42 bpm) with evident atrio-ventricular dissociation.

 


Images 3 and 4: color M-mode tracing demonstrating both the flow in the left atrium and the aortic outflow, also confirming the regularity of both atrial and ventricular contractions with different rates being much slower at ventricular level. Note also the atrio-ventricular dissociation.

 


Images 5 and 6: simultaneous pulsed wave insonation of both left ventricular inflow and outflow demonstrating the atrio-venticular dissociation with the slow ventricular rate. Note that one of the atrial contractions was not evident on the trace (red star) as it occurred during closure of the mitral valve. Note also, the absence of E wave in the mitral inflow waveform that accidentally occurred prior to a ventricular contraction.

 


Images 7 to 11: simultaneous Doppler insonation of both the ascending aorta and SVC demonstrating both the forward flow in the ascending aorta and the reversed component of venous flow in the SVC occurring during the phase of atrial contraction. The trace clearly demonstrates the atrio-ventricular dissociation and both the atrial and the ventricular rates. Note in images 9 and 10, atrial contractions which are synchronous with ventricular contractions are taller (Canon A waves).

  


Videos 2, 3, 4, 5: demonstrate the structural integrity of the fetal heart including the normal situs and the concordant atrio-ventricular and ventriculo-arterial connections denoting absence of any structural defects in the heart which is a very important prognostic factor in cases of complete heart block. Note the cardiomegaly and the vigorous systolic arterial distension of aorta and pulmonary arteries.

  


Video 6: four chamber view with color Doppler clearly showing the left and right ventricular inflow pattern and the evident regurgitation across both tricuspid and mitral valves.





References:
 
1.  Hunter LE, Simpson JM. Atrioventricular block during fetal life. J Saudi Heart Assoc 2015; 27:164-178
 
2. Lopes LM, Tavares GM, Damiano AP, Lopes MA, Aiello VD, Schultz R, Zugaib M. Perinatal outcome of fetal atrioventricular block: one-hundred-sixteen cases from a single institution. Circulation 2008; 118:1268-75.
3. Simpson JM. Fetal arrythmias. Ultrasound Obstet Gynecol 2006; 27:599-606.

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