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HEART BLOCKS

HEART BLOCKS. CHAPTER 5. INTRODUCTION TO HEART BLOCKS. OCCUR WHEN THERE IS A PARTIAL OR COMPLETE INTERRUPTION IN THE CARDIAC ELECTRICAL CONDUCTION SYSTEM. CAN OCCUR ANYWHERE IN THE ATRIA BETWEEN THE SA NODE AND THE AV JUNCTION. IN THE VENTRICLES BETWEEN THE AV JUNCTION AND PURKINJE FIBERS.

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HEART BLOCKS

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  1. HEART BLOCKS CHAPTER 5 For more medical presentations - www.pmcosa.com

  2. INTRODUCTION TO HEART BLOCKS • OCCUR WHEN THERE IS A PARTIAL OR COMPLETE INTERRUPTION IN THE CARDIAC ELECTRICAL CONDUCTION SYSTEM. • CAN OCCUR ANYWHERE IN THE ATRIA BETWEEN THE SA NODE AND THE AV JUNCTION. • IN THE VENTRICLES BETWEEN THE AV JUNCTION AND PURKINJE FIBERS. For more medical presentations - www.pmcosa.com

  3. THE APPEARANCE OF THE P WAVE AND QRS COMPLEX VARIES, DEPENDING ON THE TYPE OF HEART BLOCK. RATE AND RHYTHM MAY VARY. LOCATION OF THE BLOCK AND PATIENT SYMPTOMS DETERMINE IF THE DYSRHYTHMIA IS LETHAL. For more medical presentations - www.pmcosa.com

  4. FIRST-DEGREE HEART BLOCK • DELAY OF IMPULSE BETWEEN THE ATRIA AND BUNDLE OF HIS. • OCCURS WHEN THERE IS A PARTIAL INTERRUPTION ANYWHERE IN THE ATRIAL OR AV JUNCTIONAL CONDUCTION SYSTEM. • THE IMPULSE IS EVENTUALLY CONDUCTED BUT IS DELAYED. For more medical presentations - www.pmcosa.com

  5. FIRST-DEGREE BLOCK IS NOT A TRUE BLOCK BUT SIMPLY A DELAY IN THE ELECTRICAL CONDUCTION SYSTEM. PROLONGED PRI GREATER THAN 0.20 SECONDS. THE P WAVE OCCURS BEFORE EVERY QRS BUT THE PRI IS ALWAYS GREATER THAN 0.20 SECONDS. P TO P AND R TO R INTERVALS ARE USUALLY REGULAR DEPENDING ON THE UNDERLYING RHYTHM. For more medical presentations - www.pmcosa.com

  6. MAY BE FOUND IN ANY RHYTHM THAT HAS A P WAVE BEFORE THE QRS COMPLEX. RATE MAY BE NORMAL, BRADYCARDIC, TACHYCARDIC. MUST IDENTIFY THE UNDERLYING RHYTHM FIRST. USUALLY NOT SERIOUS BUT MUST BE ASSESSED. THE PATIENT’S MYOCARDIUM MAY HAVE BEEN DAMAGED. MAY BE CAUSED BY M.I. OR DRUGS. For more medical presentations - www.pmcosa.com

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  8. MOBITZ I HEART BLOCK • MOBITZ I ( WENCKEBACH OR SECOND-DEGREE HEART BLOCK, TYPE I). • PROGRESSIVE BLOCK. • IMPULSE FROM THE ATRIA IS INTERRUPTED AT THE AV JUNCTION. • THE INTERRUPTION BECOMES LONGER WITH EACH IMPULSE DELAYING DEPOLARIZATION OF THE VENTRICLES UNTIL A COMPLETE INTERRUPTION BLOCKS THE IMPULSE. For more medical presentations - www.pmcosa.com

  9. THE CYCLE OF PROGRESSIVELY DELAYED CONDUCTION IS THEN REPEATED. THE PRI BECOMES LONGER WITH EACH QRS UNTIL A DROPPED QRS OCCURS. THE P WAVE IS SEEN WITHOUT A QRS COMPLEX. A QRS FOLLOWS EACH P WAVE UNTIL A QRS IS DROPPED. For more medical presentations - www.pmcosa.com

  10. THE OVERALL RHYTHM IS IRREGULAR. THE RATE MAY VARY. NOT A LETHAL DYSRHYTHMIA, THE PATIENT MAY BECOME MEDICALLY UNSTABLE. MAY BE SERIOUS WHEN IT INDICATES A RECENT CHANGE IN THE CONDUCTION SYSTEM FOLLOWING INJURY TO THE CARDIAC MUSCLE. MAY BE CAUSED BY INFECTION, M.I., DRUG TOXICITY. For more medical presentations - www.pmcosa.com

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  12. MOBITZ II HEART BLOCK • OCCURS DUE TO AN INTERMITTENT INTERRUPTION NEAR OR BELOW THE AV JUNCTION. • INTERRUPTION IS NOT PROGRESSIVE, BUT OCCURS SUDDENLY AND WITHOUT WARNING!! • P WAVES BEFORE EVERY QRS COMPLEX AND ALL ARE THE SAME SIZE AND SHAPE. For more medical presentations - www.pmcosa.com

  13. THIS OCCURS UNTIL A QRS COMPLEX IS DROPPED. THE QRS MAY BE WIDER IF THE BLOCK OCCURS NEAR THE BUNDLE OF HIS. CAN OCCUR IN ANY RHYTHM, OVERALL RHYTHM IS IRREGULAR AND THE HEART RATE VARIES DEPENDING ON THE UNDERLYING RHYTHM. For more medical presentations - www.pmcosa.com

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  15. INTERPRETING THE BLOCK • IDENTIFY THE UNDERLYING RHYTHM. • DETERMINE THE RATIO OF P WAVES TO QRS COMPLEXES. THIS DETERMINES THE BLOCK. 2:1 BLOCK= 2 P WAVES TO 1 QRS, 3:1 BLOCK= 3 P WAVES TO 1 QRS. • DETERMINE THE FREQUENCY OF OCCURRENCE. MAY OCCUR AT RANDOM OR IN A PATTERN. For more medical presentations - www.pmcosa.com

  16. A MOBITZ II WITH NO PATTERN (VARYING BLOCK) IS MORE DANGEROUS. THIS INDICATES THE BLOCK IS IRREGULAR AND MAY PROGRESS INTO A MORE SERIOUS DYSRHYTHMIA. THIS IS A DANGEROUS BLOCK. THE MYOCARDIUM IS INCREASED IRRITABILITY. IF THE BLOCK IS SEVERE, THE VENTRICULAR RATE MAY BECOME BRADYCARDIC. For more medical presentations - www.pmcosa.com

  17. A VENTRICULAR RATE OF 40 IMPULSES OR LESS IS NOT SUFFICIENT TO MAINTAIN ADEQUATE CIRCULATION TO THE ORGANS AND BODY. FREQUENT ASSESSMENT IS IMPORTANT TO DETERMINE THE PATIENT’S TOLERANCE OF THE DYSRHYTHMIA. CAUSED BY M.I., HEART DISEASE, OR DRUG TOXICITY. For more medical presentations - www.pmcosa.com

  18. THIRD-DEGREE HEART BLOCK • COMPLETE HEART BLOCK OR COMPLETE AV DISSOCIATION. • IMPULSE IS COMPLETELY BLOCKED BETWEEN THE ATRIA AND THE VENTRICLES. • USUALLY TAKES PLACE BETWEEN THE AV JUNCTION AND BUNDLE OF HIS. For more medical presentations - www.pmcosa.com

  19. THE VENTRICLES MUST INITIATE THEIR OWN IMPULSES. THE ATRIA AND VENTRICLES ARE FUNCTIONING INDEPENDENTLY! PR INTERVALS ARE CONSTANTLY CHANGING IN LENGTH. THE INTERVALS DO NOT BECOME PROGRESSIVLY LONGER AS THEY DO IN MOBITZ I NO TRUE PR INTERVAL OCCURS. For more medical presentations - www.pmcosa.com

  20. P WAVES AND QRS COMPLEXES APPEAR AS WELL AS PR INTERVAL THAT ARE CONSTANTLY CHANGING IN LENGTH. THE PRI’S DO NOT BECOME PROGRESSIVELY LONGER. NO RELATIONSHIP EXISTS BETWEEN THE P WAVES AND QRS COMPLEXES. NO TRUE PR INTERVAL. For more medical presentations - www.pmcosa.com

  21. THE QRS COMPLEXES ARE WIDE AND BIZZARE WITH A TIME FRAME OF >0.12 SECONDS. DEPOLARIZATION IS AT THE INHERENT RATE BUT THE P TO P AND R TO R INTERVALS ARE NOT EQUAL. ATRIAL RATE 60 TO 100 VENTRICULAR RATE 20 TO 40. THIS IS A LETHAL DYSRHYTHMIA. CAN LEAD TO ASYSTOLE. For more medical presentations - www.pmcosa.com

  22. Third degree heart block For more medical presentations - www.pmcosa.com

  23. BUNDLE BRANCH BLOCK (BBB) • INTERRUPTION IN THE ELECTRICAL CONDUCTION SYSTEM OF EITHER THE RIGHT, LEFT OR BOTH BUNDLE BRANCHES. • CAUSES A DELAY TO THE VENTRICLES. • THE INTERRUPTION FORCES THE IMPULSE TO “DETOUR” AND TAKE ANOTHER ROUTE TO THE VENTRICLES. For more medical presentations - www.pmcosa.com

  24. THIS EXTRA TIME CAUSES THE IMPULSE TO REACH THE VENTRICLE LATER. THIS CAUSES TWO SEPARATE DEPOLARIZATIONS. THE RHYTHM STRIP HAS A NOTCHED QRS REFERRED TO AS “RABBIT EARS”. THE QRS MEASURES WIDER THAN 0.12 SECONDS. IF BOTH BRANCHES ARE BLOCKED THE IMPULSE TAKES LONGER TO REACH THE VENTRICLES. For more medical presentations - www.pmcosa.com

  25. BBB MAY OCCUR IN ANY RHYTHM. P WAVES AND PRI IS DETERMINED BY THE UNDERLYING RHYTHM. YOU MUST IDENTIFY THE UNDERLYING RHYTHM FIRST. ARE NOT LETHAL DYSRHYTHMIAS. A 12-LEAD EKG IS REQUIRED TO DETERMINE IF THE BLOCK IS IN THE RIGHT OR LEFT BUNDLE BRANCH. For more medical presentations - www.pmcosa.com

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  27. MANAGEMENT • BRADYDYSRHYTHMIAS PRESENT THE THREAT OF IMPAIRED CARDIAC OUTPUT RESUTLING IN CARDIOGENIC SHOCK AND POSSIBLE DEATH. • IN 1ST AND 2ND DEGREE BLOCKS THE PATIENT IS USUALLY PERFUSING ADEQUATELY. For more medical presentations - www.pmcosa.com

  28. THERAPEUTIC MANAGEMENT WILL RESULT IN AN INCREASE IN RATE. THE INCREASED RATE WILL DIRECTLY INCREASE MYOCARDIAL OXYGEN DEMAND. PATIENTS ARE MANAGED ONLY IF THEY ARE HEMODYNAMICALLY SYMPTOMATIC. THESE ARE SHOCK SYMPTOMS DUE TO LACK OF CARDIOVASCULAR PERFUSION. For more medical presentations - www.pmcosa.com

  29. SHOCK SYMPTOMS: DIMINISHED LEVEL OF CONSCIOUSNESS DIAPHORESIS FATIGUE DYSPNEA MUCOSA AND NAIL BED BLANCHING For more medical presentations - www.pmcosa.com

  30. POSSIBLE MANAGEMENT SOLUTIONS • 1ST DEGREE BLOCK – ASSESS AND MONITOR THE PATIENT. • MOBITZ I ( 2ND DEGREE, TYPE I) – USUALLY DOES NOT REQUIRE TREATMENT, BUT IF THE PATIENT IS MEDICALLY UNSTABLE OR POOR CARDIAC OUTPUT ATROPINE IS USED IF THE OVERALL RATE IS BRADYCARDIC. For more medical presentations - www.pmcosa.com

  31. MOBITZ II (2ND DEGREE, TYPE II) – OXYGEN, IV FLUIDS, ATROPINE IF OVERALL RATE IS BRADYCARDIC, ARTIFICIAL PACEMAKER, DOPAMINE OR EPINEPHRINE. IF HEART RATE IS GREATER THAN 100 BUT LESS THAN 150 DILTIAZEM, DIGOXIN, OR BETA BLOCKERS. 3RD DEGREE BLOCK – OXYGEN, IV FLUIDS, ATROPINE IF BRADYCARDIC, DOPAMINE, EPINEPHRINE, OR ARTIFICIAL PACEMAKER. BBB- PATIENT ASSESSMENT For more medical presentations - www.pmcosa.com

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