Introductory and personal note
Five plus years ago I experienced a sudden decrease in my exercise ability.As a long time marathon runner I was well aware of running times and perceived exertional sensation for various speeds. My running times decreased by about 15% (comparing times for a one mile run at a comfortable pace).
My EKG at my internist's office show an LBBB pattern. Neither he nor I were aware of the significant exercise impairment that can be caused by LBBB. A number of web sites even now offer misinformation about LBBB. Over the past five years there has been much learned about LBBB,His Bundle Pacing,and the potentially harmful effects of pacing the heart from the right apex, and the entity of LBBB induced cardiomyopathy.
I also had developed an exercise induced high grade second degree heart block for which I received a pacemaker ( PM) importantly with a Bundle of His lead (HB) After recovery from the implantation procedure I was able to return to running with an apparent recovery to my pre LBBB level. A number of blog readers have contacted me about exercise problems similar to mine and their frustration with the medical advice from their cardiologists. I was evaluated for coronary artery disease and none was found.(see endnote 1)
The following is a recap of what I have learned about LBBB and related matters which may be of interest at least to folks with that condition. It is not offered as specific medical advice and is just my take on a subject of obvious great personal importance from a non-cardiologist who over the last five years has enjoyed a non-sanctioned,personal,perhaps quiky ,self directed mini fellowship in electrophysiology.
____
All LBBBs are not created equal. Even the subset of lone LBBB is not homogenous.
About half of patients whose EKGs meet standard criteria for LBBB are shown to have a particular pattern on echocardiography.This seems to be the case whether the standard criteria are used or the more stringent Strauss criteria.(see end note 2)
This echo pattern describes an abnormal,out- of -sync contraction pattern of the left ventricule (LV)
It begins with a electrical activation of the interventricular septum from right to left (opposite to the normal direction of septal activation) and then a swift leftward movement of the septum and a bulging out of the left lateral ventricular wall,followed by a delayed LV wall contraction and rightward bulging of the septum.The septal movement occurs before the aortic valve opens (in the isovolemic contraction phase when mitral and aortic valves are closed as pressure builds up to snap open the aortic valve).Some ,but not all, patients with an EKG pattern of LBBB demonstrate this pattern on echocardiography or Cardiac MRI studies
This same pattern has been observed in at least some cases of RV apical pacing.
Cramer and De Boeck (1)et al describe this mechanism by which abnormal electrical activation leads to abnormal contraction-a dyscoordination of contraction in at least many cases of LBBB.
" This discoordination encompasses regional differences in timing,duration and amplitudes of contraction.When the differences are large enough,part of the contractile energy of the early contracting segments will be dissipated into abnormal stretching of remote areas during early systole and vice versa at end systole...The decreased global pump function will activate neurohormonal response mechanisms in an attempt to maintain normal cardiac output,favouring ventricular dilatation and remodeling. "
In some patients, LBBB is not associated with this pattern and in these it may be that electrical signals are merely delayed but occur in the normal left to right pattern .Several patterns of septal motion have been described.
The resting echo typically demonstrates no problem other than an ejection fraction (EF) that might be at the lower limits of normal and in the absence of a earlier higher value carries little diagnostic value.However some work indicates that the ejection fraction is not accurately measured in LBBB using the Simpson method and that the "true" EF is lower than measured.
It should be noted that it may be possible to recognize the early left ward motion of the septal on echo and has been named "septal flash".Patients with this septal flash pattern generally respond well and sometimes exceptionally well with CRT-either with traditional bi-ventricular CRT or with His Bundle pacing.
With exercise, stroke volume fails to increase ,diastolic pressures rise and the patient may become short of breath. Human and animal work have demonstrated that increased afterload (as with increased blood pressure) and increased heart rate cardiac function decreases significantly including decrease in EF.
A patient presenting to a cardiology clinic with LBBB,no symptoms and a negative evaluation for coronary artery disease would likely be reassured and followed.
A symptomatic patient poses a more difficult problem.If he had a normal echo some docs would just follow the patient , a management plan not likely to be well received by an endurance athlete.If the patient had reached a phase of cardiomyopathy with evidence of heart failure, the usual medications would likely be prescribed .However reports indicate that the usual goal directed therapy GRT) is not effective in LBBB induced cardiomyopathy.Some authors have suggested that earlier (that is less than the standard three month trial of GDT) pacemaker therapy should be used.
Five years ago His Bundle pacing was not a routine procedure for PM implantation- now it has become the default procedure in a number of centers for AV block and for sinus node disease and for pacing after A-V node ablation and in some centers the preferred approach for CRT instead of Left ventricular pacing through a lead in the coronary sinus.
end note 2
Strauss criteria for EKG diagnosis of LBBB- QRS greater than 140 msec in males,and greater than 130 msec in women and mid QRS notching in 2 contiguous leads.(Strauss,D Defining Left bundle branch block in the era of Cardiac Resynchronization Therapy. Am J Cardiology 107 (6)2011
My EKG at my internist's office show an LBBB pattern. Neither he nor I were aware of the significant exercise impairment that can be caused by LBBB. A number of web sites even now offer misinformation about LBBB. Over the past five years there has been much learned about LBBB,His Bundle Pacing,and the potentially harmful effects of pacing the heart from the right apex, and the entity of LBBB induced cardiomyopathy.
I also had developed an exercise induced high grade second degree heart block for which I received a pacemaker ( PM) importantly with a Bundle of His lead (HB) After recovery from the implantation procedure I was able to return to running with an apparent recovery to my pre LBBB level. A number of blog readers have contacted me about exercise problems similar to mine and their frustration with the medical advice from their cardiologists. I was evaluated for coronary artery disease and none was found.(see endnote 1)
The following is a recap of what I have learned about LBBB and related matters which may be of interest at least to folks with that condition. It is not offered as specific medical advice and is just my take on a subject of obvious great personal importance from a non-cardiologist who over the last five years has enjoyed a non-sanctioned,personal,perhaps quiky ,self directed mini fellowship in electrophysiology.
____
All LBBBs are not created equal. Even the subset of lone LBBB is not homogenous.
About half of patients whose EKGs meet standard criteria for LBBB are shown to have a particular pattern on echocardiography.This seems to be the case whether the standard criteria are used or the more stringent Strauss criteria.(see end note 2)
This echo pattern describes an abnormal,out- of -sync contraction pattern of the left ventricule (LV)
It begins with a electrical activation of the interventricular septum from right to left (opposite to the normal direction of septal activation) and then a swift leftward movement of the septum and a bulging out of the left lateral ventricular wall,followed by a delayed LV wall contraction and rightward bulging of the septum.The septal movement occurs before the aortic valve opens (in the isovolemic contraction phase when mitral and aortic valves are closed as pressure builds up to snap open the aortic valve).Some ,but not all, patients with an EKG pattern of LBBB demonstrate this pattern on echocardiography or Cardiac MRI studies
This same pattern has been observed in at least some cases of RV apical pacing.
Cramer and De Boeck (1)et al describe this mechanism by which abnormal electrical activation leads to abnormal contraction-a dyscoordination of contraction in at least many cases of LBBB.
" This discoordination encompasses regional differences in timing,duration and amplitudes of contraction.When the differences are large enough,part of the contractile energy of the early contracting segments will be dissipated into abnormal stretching of remote areas during early systole and vice versa at end systole...The decreased global pump function will activate neurohormonal response mechanisms in an attempt to maintain normal cardiac output,favouring ventricular dilatation and remodeling. "
In some patients, LBBB is not associated with this pattern and in these it may be that electrical signals are merely delayed but occur in the normal left to right pattern .Several patterns of septal motion have been described.
The resting echo typically demonstrates no problem other than an ejection fraction (EF) that might be at the lower limits of normal and in the absence of a earlier higher value carries little diagnostic value.However some work indicates that the ejection fraction is not accurately measured in LBBB using the Simpson method and that the "true" EF is lower than measured.
It should be noted that it may be possible to recognize the early left ward motion of the septal on echo and has been named "septal flash".Patients with this septal flash pattern generally respond well and sometimes exceptionally well with CRT-either with traditional bi-ventricular CRT or with His Bundle pacing.
With exercise, stroke volume fails to increase ,diastolic pressures rise and the patient may become short of breath. Human and animal work have demonstrated that increased afterload (as with increased blood pressure) and increased heart rate cardiac function decreases significantly including decrease in EF.
A patient presenting to a cardiology clinic with LBBB,no symptoms and a negative evaluation for coronary artery disease would likely be reassured and followed.
A symptomatic patient poses a more difficult problem.If he had a normal echo some docs would just follow the patient , a management plan not likely to be well received by an endurance athlete.If the patient had reached a phase of cardiomyopathy with evidence of heart failure, the usual medications would likely be prescribed .However reports indicate that the usual goal directed therapy GRT) is not effective in LBBB induced cardiomyopathy.Some authors have suggested that earlier (that is less than the standard three month trial of GDT) pacemaker therapy should be used.
Five years ago His Bundle pacing was not a routine procedure for PM implantation- now it has become the default procedure in a number of centers for AV block and for sinus node disease and for pacing after A-V node ablation and in some centers the preferred approach for CRT instead of Left ventricular pacing through a lead in the coronary sinus.
Although by 2000 there was great interest and enthusiasm for HBP and had become a II A AHA/ACC/HRS guideline recommendation, more recent analysis of data from HBP follow up has revealed perhaps as many as a quarter of successful His bundle implantation with adequately capture voltages over time increase voltage requirements to levels which likely will lead to premature battery replacements.This in part has lead to increasing acceptance of another,newer form of conduction system pacing namely pacing the left bundle directly by advancing a lead further into the RV apex and screwing in a lead deep into the septum. As of this writing bundle branch area pacing has become popular in China, it s country of origin, and also apparently used a a primary means of pacing in place of HBP at Virginia Commonwealth Medical School according to a recent article by Padala and Ellenbogen (2). As best I can tell as an outsider, some form of conduction system pacing has largely replaced the traditional pacing from the right ventricular apex.
1 Cramer,MMJ and De Boeck, BW Three dimensional echocardiography and left bundle branch block:Prime time in cardiology. Neth Heart J 2007 Mar 15(3) 87
2) Padala, S and Ellenbogen KA Left bundle branch pacing is the best approach to physiological pacing. Heart rhythm ,2020
end note 1
As was the party line recommendation at the time,coronary disease was evaluated by a stress echo in a patient with LBBB.Abnormal movement of the interventricular septum,decreased septal blood flow not caused by obstructive disease and abnormal changes on the ekg generally make various testing methods less than optimally reliable, eg.regular treadmill exercise and some isotope tests. The SPECT myocardial perfusion imaging is a problem because of septal perfusion defects occurring in patients who do not have obstructive lesions in the Left anterior descending artery. The stress echo test is popular in some centers but a recent review from the Cleveland Clinic discredits the stress echo considering it unreliable and favors CT angiography if patients less than 65 and the pharmacologic nuclear imaging or dobutamine stress echocardiography if over 65 years of age.Older patients are more likely to have coronary calcification making the CT angio less useful. (.https://consultqd.clevelandclinic.org/in-patients-with-left-bundle-branch-block-whats-the-best-test-for-cad/)
1 Cramer,MMJ and De Boeck, BW Three dimensional echocardiography and left bundle branch block:Prime time in cardiology. Neth Heart J 2007 Mar 15(3) 87
2) Padala, S and Ellenbogen KA Left bundle branch pacing is the best approach to physiological pacing. Heart rhythm ,2020
end note 1
As was the party line recommendation at the time,coronary disease was evaluated by a stress echo in a patient with LBBB.Abnormal movement of the interventricular septum,decreased septal blood flow not caused by obstructive disease and abnormal changes on the ekg generally make various testing methods less than optimally reliable, eg.regular treadmill exercise and some isotope tests. The SPECT myocardial perfusion imaging is a problem because of septal perfusion defects occurring in patients who do not have obstructive lesions in the Left anterior descending artery. The stress echo test is popular in some centers but a recent review from the Cleveland Clinic discredits the stress echo considering it unreliable and favors CT angiography if patients less than 65 and the pharmacologic nuclear imaging or dobutamine stress echocardiography if over 65 years of age.Older patients are more likely to have coronary calcification making the CT angio less useful. (.https://consultqd.clevelandclinic.org/in-patients-with-left-bundle-branch-block-whats-the-best-test-for-cad/)
end note 2
Strauss criteria for EKG diagnosis of LBBB- QRS greater than 140 msec in males,and greater than 130 msec in women and mid QRS notching in 2 contiguous leads.(Strauss,D Defining Left bundle branch block in the era of Cardiac Resynchronization Therapy. Am J Cardiology 107 (6)2011
No comments:
Post a Comment