Mobitz Type I

[Dave__0__0]

  A year ago I was diagnosed with Mobitz Type I AV Node block. This was
  during a medical for a private pilots license. After a lot of indecision
  I was certified to fly, caveat that I have a yearly holter monitor that
  does not show more than 1 consecutive dropped P-wave. Incidently I know
  I have had this condition for most of my life (37 yo) - it has never been
  a problem - I am asymptomatic.
  Needless to say my last holter showed 3 consecutive dropped p-waves giving
  a pause of 3.7 seconds.
  However this occured at 5am (definitely asleep!!!) at a heart rate of
  70bpm. This was unusually high - the rate was mostly less than 40bpm while
  sleeping. Also on the strip there was a large amount of noise(?) which
  the p-waves were only just distinguishable above only during that pause.
  Has there been any research carried out on the influence of sleep patterns
  on the AV node/Vagal Tone. ie. How relevant is monitoring during sleep?

[CCF Cardio MD - MTR]

Dear Dave, thank you for your question. The only published study that I could find regarding the influence of sleep patterns on AV node function is attached to this response.  This study was done in patients with sleep apnea which is a condition that is usually found in obese people who transiently close their airway during sleep due to excess tissue in the throat.  Vagal tone is usually at the highest level during sleep and it's not uncommon to have pauses like you mentioned.  The significance of the pauses seen on your Holter Monitor is unclear, but I doubt that these pauses are anything to worry about.  Mobitz I AV block is considered to be a benign rhythm disorder, but the significance of this and the pauses found on your Holter monitor will have to be determined by your own physician.
I hope this information is useful. Information provided in the heart forum is for general purposes only.  Only your physician can provided specific diagnoses and therapies.  Feel free to write back with further questions. Good luck!
If you would like to make an appointment at the Cleveland Clinic Heart Center, please call 1-800-CCF-CARE or inquire online by using the Heart Center website at www.ccf.org/heartcenter.   The Heart Center website contains a directory of the cardiology staff that can be used to select the physician best suited to address your cardiac problem.
Unique Identifier
98211474
Authors
Koehler U.  Fus E.  Grimm W.  Pankow W.  Schafer H.  Stammnitz A.  Peter JH.
Institution
Dept of Internal Medicine, Schlafmedizinisches Labor, Philipps-University Marburg, Germany.
Title
Heart block in patients with obstructive sleep apnoea: pathogenetic factors and effects of treatment.
Source
European Respiratory Journal.  11(2):434-9, 1998 Feb.
Local Messages
Abstract
Heart block during sleep has been described in up to 10% of patients with obstructive sleep apnoea. The aim of this study was to determine the relationship between sleep stage, oxygen desaturation and apnoea-associated bradyarrhythmias as well as the effect of nasal continuous positive airway pressure (nCPAP)/nasal bi-level positive airway pressure (nBiPAP) therapy on these arrhythmias in patients without electrophysiological abnormalities. Sixteen patients (14 males and two females, mean age 49.6+/-10.4 yrs) with sleep apnoea and nocturnal heart block underwent polysomnography after exclusion of electrophysiological abnormalities of the sinus node function and atrioventricular (AV) conduction system by invasive electrophysiological evaluation. During sleep, 651 episodes of heart block were recorded, 572 (87.9%) occurred during rapid eye movement (REM) sleep and 79 (12.1%) during nonrapid eye movement (NREM) sleep stages 1 and 2. During REM sleep, the frequency of heart block was significantly higher than during NREM sleep: 0.69+/-0.99 versus 0.02+/-0.04 episodes of heart block x min(-1) of the respective sleep stage (p<0.001). During apnoeas or hypopnoeas, 609 bradyarrhythmias (93.5%) occurred with a desaturation of at least 4%. With nCPAP/ nBiPAP therapy, apnoea/hypopnoea index (AHI) decreased from 75.5+/-39.6 x h(-1) to 3.0+/-6.6 x h(-1) (p<0.01) and the number of arrhythmias from 651 to 72 (p<0.01). We conclude that: 1) 87.9% of apnoea-associated bradyarrhythmias occur during rapid eye movement sleep; 2) the vast majority of heart block episodes occur during a desaturation of at least 4% without a previously described threshold value of 72%; and 3) nasal continuous positive airway pressure or nasal bi-level positive airway pressure is the therapy of choice in patients with apnoea-associated bradyarrhythmias.