A Case of Dizziness. A 68 year old female arrives at the emergency room in an ambulance. That evening she had been feeling “weak and dizzy” after ingesting a handful of her “heart pills” and later passed out. Her heart rate was irregular but near 33 beats per minute. - PowerPoint PPT Presentation
A Case of Dizziness A Case of Dizziness A 68 year old female arrives at the emergency room in an ambulance. That evening she had been feeling “weak and dizzy” after ingesting a handful of her “heart pills” and later passed out. Her heart rate was irregular but near 33 beats per minute. Her patient records and talks with her family revealed that she is being treated for poorly controlled hypertension and congestive heart failure. Her records indicate she has been prescribed the following medications: Doxazosin Avapro Tiazac Toprol Lasix Potassium supplements Digoxin Zyrtec, celebrex
Transcript
A Case of DizzinessA Case of DizzinessA 68 year old female arrives at the emergency room in an ambulance. That evening she had been feeling “weak and dizzy” after ingesting a handful of her “heart pills” and later passed out. Her heart rate was irregular but near 33 beats per minute.
Her patient records and talks with her family revealed that she is being treated for poorly controlled hypertension and congestive heart failure. Her records indicate she has been prescribed the following medications:
Her EKG records displayed several arrhythmias and while efforts at treatment were being made, she went into ventricular fibrillation.
The EKGThe EKG
Physiology in action
ObjectivesObjectives
understand basic cardiac anatomy understand how cellular action potentials give
rise to a signal that can be recorded with extracellular electrodes
understand the path for action potential propagation through the heart
understand the origin of the main phases of electrocardiogram (EKG)
The HeartThe Heart
is a pump
has electrical activity(action potentials)
generates electricalcurrent that can be measured on the skin surface (the EKG)
Currents and VoltagesCurrents and Voltages
At rest, Vm is constant No current flowing Inside of cell is at
constant potential Outside of cell is at
constant potential
++++++++++++++++++
------------------------------
A piece of cardiac muscle
outside
inside
0 mV
+-
Currents and VoltagesCurrents and Voltages
During AP upstroke, Vm is NOT constant
Current IS flowing Inside of cell is NOT at
constant potential Outside of cell is NOT
at constant potential
++++------------------------------++++++++++++++
A piece of cardiac muscle
outside
inside
Some positive potential+-
current
AP
An action potential propagatingtoward the positive ECG lead produces a positive signal
More Currents and VoltagesMore Currents and VoltagesA piece of cardiac muscle
outside
current
+-
A negative voltage reading
------++++++++++++++
inside
++++------------------------An action potential propagatingAway from the positive ECG lead produces a negative signal
More Currents and VoltagesMore Currents and Voltages
current
-------------------------------
A piece of totally depolarizedcardiac muscle
outside
inside+++++++++++++++++++
Vm not changingNo currentNo ECG signal
+++++++-------------------
A piece of cardiac muscle
outside
inside------------+++++++++++
During Repolarization
+-Some negative potential
Repolarization spreading towardthe positive ECG lead producesa negative response
The EKGThe EKG Can record a reflection of cardiac electrical
activity on the skin- EKG The magnitude and polarity of the signal depends
on– what the heart is doing electrically
depolarizing repolarizing whatever
– the position and orientation of the recording electrodes
Cardiac AnatomyCardiac Anatomy
Atrial muscleSinoatrial (SA)A node Left atrium
Descending aortaInferiorvena cava
Ventricluar
Pulmonaryveins
Superiorvena cava
Tricuspid valve
Mitral valve
Atrioventricular (AV) node
Purkinjefibers
muscle
Internodalconducting
tissue
Flow of Cardiac Electrical Flow of Cardiac Electrical ActivityActivity
SA node Atrial muscle
AV node (slow)
Purkinje fiberconducting system Ventricular muscle
Internodalconductingfibers
Atrial muscle
Conduction in the HeartConduction in the Heart0.12-0.2 s approx. 0.44 s
SA
AtriaAtrial muscleSA node Left atrium
Descending aortaInferiorvena cava
Ventricluar
Pulmonaryveins
Superiorvena cava
Tricuspid valve
Mitral valve
AV node
Purkinjefibers
muscle
Specializedconducting
tissue
Purkinje
Ventricle
node
nodeAV
The Normal EKGThe Normal EKG
P
Q
R
S
T
Right Arm
Left Leg
QTPR
0.12-0.2 s approx. 0.44 s
Atrial muscledepolarization
Ventricular muscledepolarization
Ventricular musclerepolarization
“Lead II”
Action Potentials in the HeartAction Potentials in the Heart
AV
Purkinje
Ventricle
Aortic artery
Left atrium
Descending aortaInferiorvena cava
Ventricluar
Atrial muscle
Pulmonaryveins
Superiorvena cava
Pulmonary artery
Tricuspid valve
Mitral valve
Interventricularseptum
AV nodeSA node
ECGQTPR
0.12-0.2 s approx. 0.44 s
SA
Atria
Purkinjefibers
muscle
Specializedconducting
tissue
Start of EKG CycleStart of EKG Cycle
Early P WaveEarly P Wave
Later in P WaveLater in P Wave
Early QRSEarly QRS
Later in QRSLater in QRS
S-T SegmentS-T Segment
Early T WaveEarly T Wave
Later in T-WaveLater in T-Wave
Back to where we startedBack to where we started
A Case of Sudden DeathA Case of Sudden DeathA 68 year old female arrives at the emergency room in an ambulance. That evening she had been feeling “weak and dizzy” after ingesting a handful of her “heart pills” and later passed out. Her heart rate was irregular but near 33 beats per minute.
Her patient records and talks with her family revealed that she is being treated for poorly controlled hypertension and congestive heart failure. Her records indicate she has been prescribed the following medications:
Her EKG records displayed several arrhythmias and while efforts at treatment were being made, she went into ventricular fibrillation.
A Case of Sudden DeathA Case of Sudden DeathAs noted, the patient’s heart rate was irregular and so were her EKG records. The figures below show two types of patterns seen:
