Chapter14

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

Chapter 14 : 

Chapter 14 ST Segment and T Waves

Basics : 

Basics  ST segment represents section of complex in which ventricles are between electrical depolarization and repolarization Measured from J point to beginning of T wave Measurement usually approximate because: J point is not sharp. Beginning of T wave is not clearly visible.

The ST Segment : 

The ST Segment

Sharp and Diffuse J Points : 

Sharp and Diffuse J Points The J point can be sharp and clearly defined, or or diffuse.

ST Segment and T Wave : 

ST Segment and T Wave Together, ST segment and T wave are important aspects of ECG to master: This is the area that reflects ischemic insult or injury to myocardium. ST depression and T waves in opposite direction from normal = ischemia ST elevation, with or without T wave changes = myocardial injury

The J Point : 

The J Point J point: Where transition occurs between the QRS complex and ST segment Easily identified in most ECGs On some you can only isolate an area where the J point should be found. Diffuse J points are associated with: Early repolarization LVH with strain Pericarditis Sometimes AMIs

Sharp vs. Diffuse J Points : 

Sharp vs. Diffuse J Points

ST Segment Elevation or Depression (1 of 2) : 

ST Segment Elevation or Depression (1 of 2) Key aspect to identify when examining an ST segment is its relationship to the baseline. This will determine presence of ST elevation or depression.  Critical Determination  Baseline is measured from TP segment to TP segment. In certain cases, the TP segment is difficult to identify (T and P waves overlap). Use your best judgment and PR interval to determine baseline.

ST Segment Elevation or Depression (2 of 2) : 

ST Segment Elevation or Depression (2 of 2) ST elevation <1mm considered normal in limb leads. V1 to V3 precordials can show elevation of 2–3 mm in LVH with strain * ANY elevation is important if it was not there on a previous ECG, or if history matches presence of ischemia.

ST Segment Shapes : 

ST Segment Shapes

ST Segment Shapes and Possible Causes : 

ST Segment Shapes and Possible Causes

T Wave Morphologies : 

T Wave Morphologies T waves can be: Short or tall Broad or narrow Symmetrical or asymmetrical Positive, negative, or biphasic Concentrate on: Shape Polarity Height or depth

T Wave Shape : 

T Wave Shape Asymmetry is normal presentation of T wave. Symmetrical T waves found in pathological states such as: Ischemia Electrolyte abnormalities CNS problems Symmetrical T waves can be normal in SOME people, but should be considered pathological until proven otherwise.

Determining Symmetry : 

Determining Symmetry Tall, narrow Ts are common in hyperkalemia. Broad T waves have been found in CNS events (eg, intracranial hemorrhage). To determine symmetry: Place hairline ruler vertically on peak of T wave. If two sides separated by dividing line are mirror images, T wave is symmetrical. If difficult: Extend two legs of T wave as straight line to baseline.

T Wave Symmetry : 

T Wave Symmetry

More Examples of T Wave Shape : 

More Examples of T Wave Shape

Biphasic T Waves (1 of 2) : 

Biphasic T Waves (1 of 2) Biphasic T waves can occur in any lead, but especially leads transitioning between + and – T wave. If first part of T wave is –, cause is more likely pathological.

Biphasic T Waves (2 of 2) : 

Biphasic T Waves (2 of 2)

T Wave Polarity : 

T Wave Polarity T waves can be +, –, or anything in between. T waves are usually: + Positive in leads I, II, and V3 to V6 – Negative in aVR +/– Variable in rest of leads If T wave is negative where it should be positive, we say T wave is flipped. Flipped T waves sometimes are indicative of ischemia or ventricular hypertrophy.

T Wave Height or Depth : 

T Wave Height or Depth T waves should not be more than: 6 mm high in limb leads 12 mm high in precordials Good rule to remember: If T wave is more than 2/3 height of R wave = Abnormal Tall T waves are associated with: Ischemia Infarction CNS events High potassium levels

T Waves : 

T Waves T wave appearance can be altered by ST segment before it: 1. Measure where T waves begin and end in a lead that shows whole wave clearly. 2. Transfer distance to lead with bizarre appearance to isolate T wave.

ECG 14-1 : 

ECG 14-1

ECG 14-6 : 

ECG 14-6

Nonspecific ST-T Wave Change : 

Nonspecific ST-T Wave Change T waves in limb leads that are flat are a sign of pathology called nonspecific ST-T wave change (NSSTTW)

A T Wave Example : 

A T Wave Example

Tall T Waves : 

Tall T Waves Tall, symmetrical T waves, especially in mid-precordials: Always think of hyperkalemia Classic hyperkalemia T wave = tall, narrow, pointed

Tombstone Segment : 

Tombstone Segment T waves that are flipped and symmetrical in leads I, aVL, and V2 to V6 = classic “tombstone” segment **Indicates large myocardial infarction**

ECG 14-17 : 

ECG 14-17

Ischemia and Injury : 

Ischemia and Injury Most important diagnosis made with ST segment and T wave Signs of ischemia: ST elevation or depression ST segment flat and/or downward sloping T wave symmetrical or, if biphasic, starts w/ negative deflection Regional distribution of ST elevation or depression affecting leads

Ischemia : 

Ischemia

Injury and/or Infarction : 

Injury and/or Infarction

ECG 14-20 : 

ECG 14-20

Strain Pattern : 

Strain Pattern Strain pattern: ST and T wave configurations that arise from repolarization abnormalities found in RVH or LVH Right ventricular strain pattern Vector in RVH gives rise to increased R wave component in V1 and V2 Increased R:S ratio would be found in RVH alone Another sign: Concave, downward, depressed ST segment and flipped, asymmetric T wave

Right Ventricular Strain Pattern (1 of 2) : 

Right Ventricular Strain Pattern (1 of 2)

Right Ventricular Strain Pattern (2 of 2) : 

Right Ventricular Strain Pattern (2 of 2) If T wave is biphasic instead of inverted, first part will usually be negative and second part positive in RVH. If first part of biphasic T wave is positive, does not necessarily signal pathology. Acute right ventricular strain can cause a rotation of heart and axis  gives rise to pattern on ECG known as S1Q3T3. S wave in lead I Q or q wave in lead III Flipped T in lead III

Criteria for RVH: Review : 

Criteria for RVH: Review Include: P-pulmonale (RAE) Right axis deviation Increased R:S ratio in V1 and V2 (most important) RVH strain pattern S1Q3T3 pattern Not all criteria have to be met, but more than one should.

RVH: Minor Criteria : 

RVH: Minor Criteria Include: Incomplete RBBB pattern R wave in V1 that is 7 mm or more S wave in V1 that is 2 mm or more qR pattern in V1

Differential Diagnosis Points for Increased R:S Ratio in V1 or V2 : 

Differential Diagnosis Points for Increased R:S Ratio in V1 or V2 Include: Right ventricular hypertrophy Right bundle branch block Posterior wall AMI WPW type A Young kids and adolescents

Left Ventricular Strain Pattern (1 of 2) : 

Left Ventricular Strain Pattern (1 of 2) Left ventricle can develop a strain pattern if there is significant hypertrophy. Caused by repolarization abnormalities of hypertrophied ventricle. Signs of LVH with strain pattern: ST depression with downward concavity Flipped and asymmetric T wave in left precordial leads of V4 to V6

Left Ventricular Strain Pattern (2 of 2) : 

Left Ventricular Strain Pattern (2 of 2) In right precordials: ST elevation with upward concavity Upright, asymmetric T wave ST elevation can be 1–3 mm in V2 to V3

Left Ventricular Strain Pattern: Key Point : 

Left Ventricular Strain Pattern: Key Point  Strain pattern is the greatest in the lead with the tallest and deepest QRS pattern.

More on LVH with Strain : 

More on LVH with Strain One of the most problematic interpretations in electrocardiography—distinguishing it from ischemia and infarction. Sharp J point is more indicative of ischemia or infarction. LVH with strain has a more diffuse J point in right precordials V1 to V3. Strain pattern in V5 to V6 may become flat or downwardly depressed.  Key Point: Somewhere in V4 to V5 area, complexes will have concavity downward and asymmetric T wave; remember “company it keeps.”

Strain vs. Infarction/Ischemia : 

Strain vs. Infarction/Ischemia

The Range of LVH With Strain : 

The Range of LVH With Strain

ECG 14-28 : 

ECG 14-28

Transitioning ST Segments and T Waves : 

Transitioning ST Segments and T Waves Transition of ST segments and T waves of precordial leads in ECG 14-28

ECG 14-34 : 

ECG 14-34

Atrial Fibrillation and Artifact : 

Atrial Fibrillation and Artifact

Pericarditis Revisited (1 of 3) : 

Pericarditis Revisited (1 of 3) Criteria for pericarditis: PR depression Diffuse ST elevation Scooping, upwardly concave ST segments Notching of end of QRS ST elevation is variable—up to 4 or 5 mm. Scooped ST segments may start at end of QRS notching. Tachycardia is usually associated with other findings.

Pericarditis Revisited (2 of 3) : 

Pericarditis Revisited (2 of 3) ST segments elevated diffusely because entire pericardium is usually irritated. Irritation causes net positivity of epicardium—expressed as ST elevation.

Pericarditis Revisited (3 of 3) : 

Pericarditis Revisited (3 of 3) Pericarditis likely when ST elevation is seen in leads I and II (scooped and upwardly concave) Then look for presence of PR depression and notching in these leads and others. **You also need a history and physical exam consistent with pericarditis!** These criteria do not have to be present in every lead, just many of them.

Pericarditis: PR Depression and Notching : 

Pericarditis: PR Depression and Notching

STs and T Waves in Blocks (1 of 2) : 

STs and T Waves in Blocks (1 of 2) Normal circumstances: Heart depolarizes from endocardium to epicardium. Epicardium is first to repolarize. Repol wave spreads inward toward endocardium. Depolarization is positive wave traveling toward electrode. This creates a positive deflection of QRS complex. Repolarization wave travels away from epicardium (and electrode).

STs and T Waves in Blocks (2 of 2) : 

STs and T Waves in Blocks (2 of 2)  A negative wave traveling away from the electrode is the same electrically as a positive wave traveling toward it—it results in a positive T wave.

Presence of BBB or VPC (1 of 3) : 

Presence of BBB or VPC (1 of 3) BBB or VPC is circumstance of pathological transmission of action potential by cell-to-cell transmission. This slows depolarization and repolarization of cells. In turn, it produces state in which pressure gradient of heart no longer alters repolarization wave front. Repolarization wave will follow depolarization wave as expected. Result: Electrode now sees positive wave coming toward it with depolarization (positive QRS) and a negative wave approaching during repolarization (negative T wave)

Presence of BBB or VPC (2 of 3) : 

Presence of BBB or VPC (2 of 3)

Presence of BBB or VPC (3 of 3) : 

Presence of BBB or VPC (3 of 3) Final word: In a BBB, T wave is always in opposite direction of terminal portion of QRS complex: discordance. If T wave travels in same direction as last part of QRS: concordance.

authorStream Live Help