Left bundle branch block- new paradigm brewing- echo plus ekg

 Left bundle branch block (LBB) has been defined by various EKG criteria. The pattern of inter ventricular and intraventricular desynchrony cannot be predicted nor the response to CRT based on the EKG..

A patient with a EKG  pattern of LBBB may have a conduction block or delay within the His Bundle system ( intra Hissian block) or distal to the His bundle or some version of a diffuse intra-ventricular conducting defect (s) .

Various criteria have been proposed by the EKG diagnosis of LBBB but no criteria offers 100% predictive value regarding response to cardiac resynchronization therapy  (CRT )but some appear better than others.

CRT is the treatment for heart failure refractory to the usual medical treatment in patients with LBBB. CRT in the form of bi-ventricular pacing is a "work around" essentially replacing one pattern of ventricular dyssynchrony with another less damaging form of non physiological pacing, while His bundle pacing is capable of correcting the abnormal conduction.

The physiological purity of His pacing is undeniable but there are problems which include technical difficulty in placing the electrode in the right place  (the His bundle is small and surrounded by fibrous tissue),  variably high capture thresholds and a certain percentage of cases which later on develop an undesirable high capture threshold.

 Incentivized by the recognition that  although His pacing was beautifully physiologic it had definite problems,  innovatively adventurous EP cardiologists discovered they could advance the catheter further towards the cardiac apex and screw the lead deeply into the interventricular septum and then could pace the left bundle branch thus fixing the LBBB with the apparently minor physiological cost of inducing a right bundle branch block. Further there appeared to be more likelihood of success   as precise localization into the His bundle was replaced by the much less technically demanding job of getting the catheter  in the left bundle branch area, There was the concern and occasional occurrence of pushing too far and placing the lead tip into the left ventricular cavity .If recognized during the procedure the lead could be safely withdrawn.Besides EP cardiologists penetrate the  atrial septum routinely  performing ablations so  poking a small whole in a septum did not appear to be a deal breaker and a some centers Left bundle branch area pacing hasr replaced His pacing.

The term "true LBBB" has been used to indicate the conduction defect that responds well to CRT ( either Bi V or conducting system pacing ( His pacing or left bundle branch area  pacing). Further True LBBB is associated with right to left activation of the interventricular septum  and a  echocardiographic finding referred to as "septal flash"

An important question is which of the several EKG criteria of LBBB best predicts who has a true LBBB and therefore a greater likelihood of benefit from CRT

Calle et al compared the new,more stringent ESC criteria ( 2021) with the older 2013 ESC criteria.They suggest that certain other criteria should be considered;delayed R wave peak time,a septal flash,apcial rocking and a specific septal strain pattern.

Calle has published several papers on this general topic and seems to consider that the echo cardiographic finding of septal flash defines the " true electromechanical LBBB substrate and is predictive of complete reversible re-modeling.

1) Calle,S Defining left bundle branch block according to the new 2021 European Society of Cardiology Criteria.Neth Heart J. 03 May 2022  in their "point of view" section

The coivid pandemic and one million U.S.deaths have waned my anti progressive,public health antibodies just a bit

 Many decades of reading libertarian and classical  liberal literature and at least semi serious reading of Austrian school economics mixed with mainline Econ101 had for the most fixed my thinking and planted some priors that seemed unlikely to be refuted.

I was disturbed by the movement in medical discourse toward something called population medicine and blogged about traditional medical ethics with a backbone of a fiduciary duty of the doctor to the patient was being challenged by a  mushy, vague admonition for the physician to be responsible not only to the patient but somehow also to be charged with a co-duty that including being responsible for the group.Some how the physician needed to treat his/her patient but to somehow work to heal the village.

Although I  once displayed a certificate of board certification in preventive medicine- a field that includes public health,I had never felt aligned either by experience or philosophical leaning to be a member of the public health tribe. Noticing that it had become an often repeated mindless expression that Disease X,Y or r Z is a public health problem  I blogged that would make nearly everything a public health problem.I do not believe that everything is a public health problem; However, if there is spread of a potentially fatal respiratory illness than is spread by the small aerosol particle routes at times by asymptomatic persons and whose spread can significantly be mitigated by wearing masks then that is a public health problem if there ever was one and covid is one for the ages.

Claims by politicians that wearing masks is just  a personal decision because it only affects the wearer's health is clearly wrong,scientifically wrong and even wrong,IMO,from a libertarian point of view.Hat tip to Nassim Taleb who pointed out the obvious that the fundamental principle of libertarianism is the non-aggression axiom, ie. one does not have to right to initiate force against another human being. The fact that the CDC echoed the pretend conservative-libertarian thought that only the wearer is affected does not make it so and may have been the most shockingly  un public health advice even issued by a public health organization .The CDC began their battle against covid with a egregious technical error in test production and 2 years later topped that with a shape shifting moral error.

All of which brings me to admitting that I have convinced myself that not just out of a survival instinct that mandating masks and vaccines is necessary much as many abrogations of individual freedoms are necessary for a civilized society,

Mandatory vaccination and mandated masing have catalyzed a definite division in libertarian circles .One academic libertarian, Jessica Flanigan Phd has written a lengthy and I think persuasive commentary supporting the idea that mandatory vaccination  is consistent with basic libertarian views .My simplistic view of her argument is that she relies mainly on the nonaggression axiom without explicitly using those words.(Her essay can be found on the HEC forum, online, August 2013 edition. )

Reason is,and ought only to be, the slave of the passions.David Hume 

Hemolysis is part of strenuous exercise - it is not a disease

 The intravascular destruction of red blood cells (rbcs) is a normal part of strenuous exercise.It is a feature not a bug of strenuous exercise.A recent review by Lippi and Sanchis-Gomar describes hemolysis as being common place in running and characterizes the intravascular hemolysis as "paraphysiological"  and is "typically mild" with average variations of hemolysis  biomarkers( serum free hemoglobin and haptoglobin) perturbated    between 1.2 and 1.8 times and "self limiting"resolving within 24 to 8 hours.

All types of repeated  strenuous exercise are associated with hemolysis but  more notably so with running usually attributed to foot strike but non contact activities including rowing,swimming and cycling are all known to cause hemolysis.

Foot strike is thought to be a major contributor in running related hemolysis as was demonstrated in an excellent cross over study of hemolysis  in  running and cycling by Telford in 2003. Tri athletes ran and  cycled at 75% of their measured 02 max and serum free hemoglobin was elevated during both activities but  there was significant drop in haptoglobin only after the running session. Methemoglobin , an indicator of oxidative stress, was elevated to the same degree after each exercise.

Red blood cell survival is significantly shorter in runners versus sedentary controls. Chromium labelled RBCs survival is 74 days in runners  versus 115  days in a sedentary control group..

This shortened life span increases need for  RBC production with an associated increase in iron utilization. The 1 to 2 mg of iron absorption per day  normally is balanced against the normal 1-2 mg of iron loss. Endurance athletes will need a larger iron intake.Iron deficiency and iron deficiency anemia have been described not only in runners but cyclists,swimmers and rowers as well is in rugby,tennis and soccer players.

A possible mechanism for increased iron loss secondary to strenuous  exercise induced hemolysis (SEIH) is the following.Hepcidin is stimulated by the increased iron in the blood.Hepcidin decreases the release of iron from duodenal cells into the blood, trapping iron in the enterocytes. These cells live only about 3 days and then shed off which is probably one mechanism by which there increased GI blood loss in runners. Hepcidin also limits iron egress from macrophages and liver cells limiting the supply of iron to the bone marrow at a time when more iron is needed. The more running,the more hepcidin release ,the more iron tapped in the duodenal enterocytes the more iron loss in the stool. So runners and other endurance athletes  loose more iron and need more iron to increase RBC production and need a higher iron intake than a sedentary person.

Arguing against the role of hepcidin  in runner's anemia is the following: Although hepcidin is definitely elevated acutely several studies have demonstrated that after a period  of time ( 1-2 weeks) the hepcidin levels return to their baseline values.So hepcidin is only transiently elevated  and other studies have demonstrated that hepcidin levels are only elevated in those persons whose ferritin levels are above 30 suggesting that the red blood cell production imperative overrides the hemolysis induced hepcidin increase and any significant exercise related cytokine increase, 

Add to that metabolic supply chain issue a vegan diet in some athletes and menstrual  blood and there is no surprise that there is  iron deficiency and iron deficiency anemia is athletes who take part in repetitive strenuous exercise 

Hemoglobinemia and hemoglobinuria were first described medically in the early 1940s with studies of cross country runners and marathoners describing march hemoglobinuria  although observation of dark urine associated with strenuous exercise was described in the 1880s.

Iron deficiency in athletes is now so well recognized that athletes themselves and coaches and sport Medine doctors all utilize the measurement of blood ferritin levels to monitor iron levels. The 2019 Olympia Committe on Physical examination for athletes including measurement of iron status .One recent study reported that 70% of professional cyclists and competitive rowers had iron deficiency by the end of their seasons. 

"Runners anemia" is the prototype  of an iron deficiency anemia brought about by  the hemolysis associated with  multiple bouts of  strenuous exercise in an individual whose iron intake does not match the increased iron needed for the increased red blood cell production needed to compensate for the shortened average life span  and GI iron loss. Runner's anemia might be more  accurately described as the anemia of repeated strenuous exercise induced hemolysis in the face of inadequate iron intake to compensate for the associated increased iron needs. Or much simply-exertional hemolysis in a person with an iron poor diet.