Sick sinus syndrome and third degree atrio ventricular block are the most important causes for bradycardia. Sick sinus syndrome predominantly involves the sinus node but often is associated with varying degrees of involvement of the atrioventricular node and rest of the conduction system. A variety of reversible, transient factors can lead to AV block and bradyarrhythmia. This include Digoxin, Ivabradine, some drugs used for management of hypertension like beta blockers and calcium channel blockers like Verapamil and Diltiazem. Many anti arrhythmics like Amiodarone can also produce slowing of heart rate.

Hypothyroidism, electrolyte abnormalities like hypokalemia and hypothermia are other factors. Certain poisons and toxins like odollum and oleander can also produce Brady arrhythmias.Certain neurological conditions and many viral fevers can produce temporary slowing of heart rate.

Inferior wall myocardial infarction can produce bradycardia and fatigue in elderly sometimes without chest pain.

Even without any apparent reason, the heart rate tend to be variable in some patients with sick sinus syndrome.Heart rate may be fairly normal on certain occasions even in symptomatic patients.

Patients with structural abnormality of the conduction system and bradycardia are unlikely to respond to drugs and usually require permanent pacemaker implantation. Those with sick sinus syndrome may require Holter monitoring to know the extent of disease and for symptomatic correlation

One has to better understand the short-, medium-, and long-term courses of SSS and their natural courses in like patients. I agree that permanent pacing may be the only safe alternative. Would need insight from patient's physicians on this question as well as expert cardiology SSS expert opinion in patient's individual case in context of her family's histories.

The only effective medical care in patients with sinus node dysfunction (SND) is correction of extrinsic causes. No treatment is required for asymptomatic patients, even if they have abnormal SN recovery times (SNRTs) or sinoatrial conduction times (SACTs). If the patient is receiving medications that can provoke sinus bradyarrhythmias (eg, beta blockers), the medications should be stopped if possible.

Acute treatment consists of atropine (0.04 mg/kg intravenously [IV] every 2-4 h) and/or isoproterenol (0.05-0.5 mcg/kg/min intravenously [IV]). In patients with bradyarrhythmias-tachyarrhythmias, the tachyarrhythmias may be controlled with digoxin, propranolol, or quinidine. However, these patients should be monitored closely with frequent Holter monitoring to ensure that the bradyarrhythmias are not exacerbated or causing symptoms (eg, dizziness, syncope, congestive heart failure); if exacerbation of arrhythmias or symptoms occur, permanent pacemaker therapy is also required.

Activity

Patients with symptomatic SND who are not on pacemaker therapy should titrate their level of activity to minimize symptoms.

Personal opinion: I give drugs that increase heart rate as ventoline tablet 2 mg twice daily or aminophylline 100 mg twice daily or tincture belladonna or isopril (isoproterenol) drops or solution if available.

Hi Mac,.. Very good question. I thank Dr koshy for nice elaborate answar. Symptomatic sick sinus syndrome usually requires pacing. Sick sinus syndrome usually manifest with the following features

Sinus bradycardia

Sinus pause and arrest

Tachy Brady syndrome

Lone AF

Above maintained conditions if present with syncope, that usually needs pacing provided there are no reversible cause. Asymptomatic sick sinus syndrome does not require pacing.

Third degree AV block usally required pacing even asymptomatic except in patient with acute inferior wall MI or Lyme's disease or some Myocarditis. Your patient will probably benifit from pacemaker implantation though improved because bradycardia and syncope may recurr unexpectedly.. Thanks

What specific medications did you give this patient?

Hi Bolade ,orciprenaline can increase pulse rate in these conditions. However it has failed to show any mortality benefit.. Thanks

Dear All

Thanks for your responses.

The patient was on Atenolol 50mg earlier which is believed have worsen the condition. At present she is stabilizing and on Amlodac 5mg, Natrilix 1.5mg, Imdur 30mg and Salbutamol 2mg for 1 week.

Her current pulse rate is 48 bpm and blood pressure 170-140/80-75 mmHg

Can she continue on these three medicines till the pacemaker is implanted?

Thanks

Dear Mac

It is difficult to answer your question about medication treatment. After all, you gave so little information about your patient. In addition to drug-induced SSS and\or AVB, she may also have hypothyroidism, or electrolyte imbalance, morphostructural or valvular heart disease. With renal insufficiency, there is a high probability of developing accumulation of drugs (atenolole). The prognosis of bradycardia due to SSS depends on the aetiology. If the underlying cause is, for example, medication, hypothyroidism or electrolyte imbalance, then the bradycardia may resolve if the triggering cause is treated or removed.

However, for most people, SSS is idiopathic and progressive, with a highly variable development of the disease.

People with SSS may also develop BTS with AF as the tachyarrhythmia, which in turn leads to an increased risk of stroke.

What is now according to the data of Echo and HM, what is the rhythm on the ECG? TSH? BNP? serum creatinine?

Thanks

Best

Dear Tatiyana Vaikhanskaya

Thanks for your response.

The patients parathyroid hormone levels are high with low serum vitamin D levels. electrolyte levels are normal, echo-cardiogram indicates degenerative chambers but valves are fine. Kidneys are alright I guess (eGFR 45). serum creatinine, CRP and ESR is slightly high. TSH is normal and BNP is not tested as of yet.

Hi Tatiyana, thanks for your nice elaborative answar. Symptomatic sick sinus syndrome always need exclusion of reversible cause like intake of betablocker, hyperkalemia, hypothyroidism before a discission of implementing a permanent pacemaker is taken. In India we find symptomatic sick sinus syndrome on many patients who is taking betablocker as anti hypertensive drug.Often their bradycardia and symptoms improve after omission of betablocker and maintained well on medical therapy without pacemaker implantation. What is your opinion about role of orciprenaline in management of sick sinus syndrome? Thanks

Dear Biswajit,

It is true that some patients develop undue sinus slowing with beta blocker. Some such patients do have early sick sinus syndrome. They require close follow up and preferably Holter monitoring. Asymptomatic sick sinus syndrome generally do not qualify for permanent pacemaker implantation irrespective of Holter findings. Orciprenaline has been found to be useful in improving heart rate in some patients but is not a recommended treatment in SSS with symptoms. Such patients do require permanent pacemaker implantation.

Hi Biswajit,

Thank you for an excellent debate and exhaustive answers. The occurrence rate of advanced AVB in patients with SSS is much higher than previously reported, and β-blocker use is an independent risk factor for advanced AVB. In Belarus, we too often see the transformation of latent SSS or AVB, which turns into a symptomatic due to taking beta blockers as a antihypertensive or anti-arrhythmic drug. However, an interesting fact is that our doctors have not prescribed atenolol for about 10 years. Cardiologists use it in a few cases. In the above case, when the AV conduction was restored after atenolol was abolished (latent AVB) but remained symptomatic compromised chronotropic sinus node function, I think the implantation of permanent dual-chamber pacemaker a highly desirable. As for orciprenaline, on my mind its purpose is an extremely narrow point of application for management some asymptomatic SSS and in my country it is not used.

Thanks to all the participants in the discussion,

Best

Hi Mac Dz, thanks for the interesting question and additional info. I agree with the answers of the respected doctors (Biswajit М. et A.George Koshy). I wish you success in the treatment of complex patients.

Best

Dear Tatiyana Vaikhanskaya, Biswajit Majumder and A. George Koshy

Many Thanks for your highly elaborative responses.

The patients current pulse rate is between 48-50 bpm. Her pulse rate has catch up from 35 to 48 in the past few days after abolishing Atenolol. I believe her pulse rate will increase even further with medication like Amlodac, Natrilix, Imdur and Salbutamol. She still does have a bit of fatigue when walking though.

However, I need to know the following:

• If her pulse rate increases to 55 bpm will she still be needing a pacemaker?
• Can she continue on Amlodac, Natrilix, Imdur and Salbutamol for life without a pacemaker if her pulse rate returns to normal (55-60 bpm)?
• Can bradycardia of pulse rate between 48-55 bpm cause damage to heart tissue or organ failure (e.g can it affect the kidneys?)?
• Her current blood pressure ranges between 140-160/75-80 mmHg. Does this have any relationship with her low pulse rate?

Dear Mac Dz,

thank you for your case.

did you perform angio for this patient? We don‘t know info about her coronary arteries, especially RCA, which supply sinus node. Cause after myocardial revascularisation patients often don’t need pacemaker implantations.

Dear Olena Gogayeva

Thanks for your response.

The patient had already undergone a coronary bypass surgery 9 years ago.

Is it safe to perform an angiogram on the patient with the current pulse rate of 48 bpm? However, her pumping function is 60%.

Dear Mac Dz,

It’s not a problem to perform angiography if a patient has temporary electrode for cardiostimulation. But you will know is everything ok with his grafts and coronary arteries.

Hi Mac,

The profound bradycardia in your patient was most likely related to Atenolol. Now that the patient is off beta blocker, it will be ideal to perform a 24 hours Holter Test to get more insights regarding the average heart rate and the longest RR interval.

I understand that the patient is in sinus rhythm and heart rate in the range of 48 to 55 is not going to produce any deleterious effects either on the heart or the kidneys.

There is no indication to perform a coronary angiogrsm as part of evaluation of the bradycardia. She can have an exercise stress testing to evaluate for chronotropic response as well as to assess the presence of significant inducible ischemia.

If an angiogrsm is indicated based on non invasive testing, it can be safely performed without a temporary pacemaker.

With systolic BP ranging between 140 and 160, in a post CABG patient, you should consider adding ACEI or ARB.

Salbutamol can be reduced and stopped.

Thanks.

Dear A. George Koshy

Many Thanks for your response & advise.

I have attached a recent ECG result for your kind reference.

Would it be possible for you to give a comment on that? (e.g. what is the degree of heart block on this result?)

Thank you Mac for posting the ECG. It looks like a 2:1 AV block (second degree, likely to be type 1 in view of narrow QRS). There are widespread diffuse ST- T changes. It is difficult to be sure if she had an old inferior wall MI.

Please repeat the ECG as diagnosis of 2:1 block is difficult from surface ECG as the timing of the second P is on top of the expected location of the T wave.

She needs evaluation for coronary artery disease in view of the ECG changes. Good to compare with previous teachings if available, as the ST - T changes are likely to be pre existing.

Also she needs a Holter evaluation to look for progression to higher grades of AV block.

Thanks

Dear A. George Koshy

Thank you so much for your response!. It was indeed helpful.

Dear Andrei G Dan

Thanks for your highly prospective response. I also do believed that this patient will be needing a cardiac pacemaker eventually.

why this case was diagnosed as SSS?

You have to exclude any reversible cause for that bradycardia beffore concluding SSS which if diagnosed pacmaker is a must.

totally agree with DR/ Andrei G Dan

Yes and No. depending on the cause of the sick sinus syndrome.

Dear Mac Dz,

Like Dr. Andrei said, it is practically reversible only when it is caused by extraneous agents like negative chronotropic drugs, but in that case, since the sinus node is not inherently "sick" (so to say), it shouldn't be technically termed Sick Sinus Syndrome.