Quiz 40: Reason for bradycardia

Called to evaluate a term, 1-day old baby for “bradycardia” (~90 bpm). EKG is given. (Clue: V1 rhythm strip provides best wave forms to evaluate).

Question: (i) What is the cause of this relative “bradycardia” in this baby? (ii) Explain why AV block is not the primary diagnosis?

Answer:

(i) Cause for “Bradycardia” is non-conducted atrial ectopies. There is an atrial ectopy after each QRS (arrows in the figure below) that is not conducted. This is a “physiologic” block because atrial ectopy is too early for the AV node to conduct. Further, the atrial ectopy depolarizes and resets the SA node (as opposed to ventricular ectopy that usually does not). Therefore, SA node fires somewhat later than usual after an atrial ectopy leading to overall slowing of heart rate.

(ii) AV block is not the primary diagnosis because the "block" is secondary to the early timing of the atrial ectopy. AV block is a physiologic event in this situation - not a block at all.

(Unfortunately, the T waves are flat leading to some confusion in recognizing the atrial ectopies).

(Click on the image to enlarge) Arrows indicate "blocked atrial ectopies"

Quiz #39: Where is the catheter?

Two sets of images are given (PA and Lateral views in each set, from the same angiogram before and during contrast injection) obtained during pre-Glenn catheterization in this patient with Tricuspid Atresia.

Questions & Answers:

1) Trace the catheter course.

Answer: IVC-RA-ASD-LA-MV-LV-VSD-RV

2) Where do you think is the tip of the catheter?

Answer: RV

3) Using the second set of images, comment on great arteries relationship? (Normal relationship or not?).

Answer: Normally-related great arteries.

4) Bonus question: Based on the above observations, what classification type of tricuspid atresia is this?

Answer: Type 1b (Tricuspid Atresia with normally-related great arteries, Small VSD and PS). See the last image for classification of Tricuspid atresia.

(Click on the image to enlarge)

(Click on the image to enlarge)

(From Moss & Adams 5^th ed. 1995. Chapter 61: Tricuspid Atresia by Dr. Rosenthal A, Dick, McD II. p 903.)

Quiz #38: EKG Answer

Question: 5-month old with Down Syndrome. 2nd Postoperative day after surgical closure of large inlet VSD. What is the diagnosis?

Answer: Wenckebach phenomenon (2nd Degree, Mobitz type 1 AV block).

Discussion:

1) There are ventricular ectopies (escape beats) after the non-conducted P waves (Large, dark arrows). These beats have confused some responders.

2) "Grouping of beats" as seen here is a feature of Wenckebach phenomenon and is helpful in gestalt recognition.

3) Remember: Shortest PR interval should be seen in the beat that immediately follows the non-conducted beat. This will help to differentiate other rhythms (e.g. 3rd degree AV block with coincidental appearance to Wenckebach, for a short time). If you look at a longer strip of EKG, 3rd AV block with betray itself.

(Click on the image to enlarge)

Quiz #37: Echo Quiz Answer

4-hr old baby with cyanosis. The following is part of the echocardiogram.

Questions:

1) What do you observe?

Answer: ASD/PFO with exclusive right to left shunting.

2) Provide at least 3 differential diagnoses for this observation.

Answer: (i) Persistent pulmonary hypertension of newborn (aka. Persistent fetal circulation), (ii) Tricuspid Atresia, (iii) TAPVR, (iv) Pulmonary Atresia with Intact ventricular septum, (v) Any condition with pulmonary hypertension in a newborn, e.g. Ebtein's anomaly with pulmonary hypertension, etc.

Quiz #36: EKG

Answer: Complete AV block

(Click on the image to enlarge)

Quiz #35: EKG - Answer

Question: 8-year old boy was referred for chest pain. What is the diagnosis?

Answer: WPW syndrome

Short PR interval and Delta wave are noted. Delta wave is somewhat atypical in appearance - as though it is a wide QRS complex. Nevertheless, it is Delta wave.

If you are interested in locating the accessory pathway, you may refer to the answer to Quiz #5. I think, it is left-sided pathway.

(Click on the image to enlarge)

Quiz #34 - Temporary Pacemaker

6 month old infant s/p AV septal defect repair. 3^rd postoperative day. Underlying rhythm was 3^rd degree AV block & probable sinus node dysfunction. The rhythm strip was printed to evaluate the temporary pacemaker.

Questions: (Answers are in red-color fonts)

What mode is being used? ….DDD

Comment about Atrial pacing, Atrial sensing and Ventricular pacing?

a.       Is the pacemaker atrial pacing properly? (Yes/No) …No (No P wave after atrial pacing spikes “AP”)

b.      Is the pacemaker atrial sensing properly? (Yes/No) …Yes (When there is a native P wave, no atrial pacing spike. Atrial sensing “AS” properly)

c.       Is the pacemaker ventricular pacing properly? (Yes/No) …Yes (QRS complex follows every ventricular pacing spike “VP”)

Quiz #33: Arterial line traces - Answer

Question:

13-year old patient who underwent repair of coarctation of aorta earlier that day has two arterial lines, right radial & left femoral. According to the reading on the monitor, apparent peak to peak pressure gradient across the coarctation repair site is 37 mmHg.

Question: Based on the traces in each arterial line, is the pressure gradient higher than, lower than or equal to 37 mmHg? Why?

Answer:

The peak to peak pressure gradient is lower than 37 mmHg. Right radial arterial line trace has a “whip”, “fling” or “standing wave” (or as Ashish puts it in sophisticated terms…”distal pulse amplication”) that artificially increases the systolic pressure. Left femoral arterial line has a more rounded peak which is characteristic of a more central arterial line trace. Since the fling or standing wave overestimates the systolic pressure in radial arterial line, gradient of overestimated. Real systolic pressure in right radial arterial line is unfortunately not possible due to technical limitations.

Ashish’s answer: Right radial artery will be higher when compared to the femoral artery BP due to distal pulse amplification. Therefore, the peak to peak pressure gradient across the coarctation site is probably less than 37 mmHg.

Systolic and diastolic arterial blood pressures are higher and lower, respectively, in radial arteries than in the aorta. This phenomenon is known as distal pulse amplification and is due to the characteristics of the vascular tree. Briefly, a pulse waveform entering the aorta is exposed to a sudden impedance change at the capillary level, resulting in a large increment in resistance and producing reflected pulse waveforms. Those waves are added to the following ones, producing higher peaks than the original aortic systolic peak at different distances from the aortic origin. This distal pulse amplification is always present when peripheral vascular resistance is high.

Reference: Peripheral arterial blood pressure monitoring adequately tracks central arterial blood pressure in critically ill patients: an observational study. Mariano Alejandro Mignini, Enrique Piacentini and Arnaldo Dubin.  Critical Care 2006;10:R43.

Quiz #31: Answer

This RA trace was recorded in cath lab under endotracheal general anesthesia.

Question: Which wave is the taller one, a wave or v wave?

Answer: a wave (See labelled images below).

RA pressure trace consists of a, c, v waves and x, y descents.

a – atrial systole (occurs immediately after P wave. Note: electrical activity precedes mechanical activity). Dotted line helps to compare the P wave to the RA waveform.

c – bulging of tricuspid valve “cusps” during onset of ventricular systole. This will appear just after LV pressure trace crosses the atrial wave.

v – venous filling (occurs during atrial diastole which is ventricular systole). Therefore, v wave should coincide with ejection phase of ventricle as shown in LV trace or PA line trace.

(Click on the image to enlarge)

Additional images from the same patient - recorded with LPA pressure in one panel and with LV pressure in the other panel. Label indicates where c wave will be expected.

Quiz #30: EKG and Doppler Trace - Answer

13 yr old girl was transferred to ICU for atrial flutter. Patient is muscle tremors and is neurologically obtunded, thought to be secondary to severe, systemic vasculitis. Figure 1 is an EKG strip from bedside monitor on the floor. Pulse oximeter trace is present in the strip as well.

In order to clarify the diagnosis, Doppler was performed with the cursor placed between mitral valve and aortic valve.

1)      What is the diagnosis?

Sinus rhythm. Muscle tremors causing fib-flutter pattern. In EKG: Hallmark of atrial fibrillation is irregularly-irregular ventricular rate (which is absent here). Also, pulse ox trace is regular and is normal, beat-to-beat. In Doppler trace: There is 1:1 relationship between mitral inflow and aortic outflow.

2)      How would you manage this?

Just get out of the way and let them manage the obtunded state and muscle tremors.

(Click on the image to enlarge)

Quiz #29: CT scan, Vacular anomaly

CT scan images from a 8-mo old boy with stridor, vomiting and weighs 5.6 kg. Figure 1 shows anterior and Left lateral views. Figure 2 shows 3D reconstruction of trachea-bronchial tree (Barium swallow was not performed in this patient).

Questions:

1) What is the arch sidedness?

2) What is the diagnosis?

3) Does the patient need intervention and why?

Answers:

1) Right aortic arch (Arrow in the last image shows indentation in trachea).

2) Double arch with ligamentous (atretic), left arch - creating a vascular ring.

3) Patient needs intervention because the patient is symptomatic and failing to thrive.

A differential interpretation for the diagnosis - Question 2 - is "Right aortic arch with left ductal ligament". Where the anterior end of the ligament is attached will determine the difference. If the ligament is attached to the ascending aorta or a branch of the aorta, it is "double arch". Alternatively, if the ligament is attached to the MPA, it is "right arch with ductal ligament". Dotted line is drawn in the images below to help to make this determination.

Arrow in the last figure indicates the indentation in trachea from right-sided arch. Similar indentation is expected in barium swallow.

Quiz #28: EKG - Answer

1)      Ventricular rate ~181/min (Measure R-R Cycle length is 660 ms. Divide this by 2, because the paper speed is 50 mm/sec, i.e. 340 ms. 60/0.34 = 176/min).

2)      Atrial rate ~363/min (Cycle length measured is 320 ms. Correcting for paper speed, i.e 160 ms. 60/0.16 = 363/min).

3)      Diagnosis: Atrial flutter with 2:1 conduction

4)      Treatment: Because the patient is somewhat unstable, synchronized DC cardioversion. May follow with a medication (probably Amiodarone) to prevent recurrence at least until patient improves hemodynamics and out of ICU.

Arrows indicate the waves recognizable as P wave. I have put arrows close together in the middle only. The presumption is one P wave hiding inside each QRS; thus preventing us from recognizing the rhythm.

When it is a 2:1 conduction, recognition alternate P waves may be difficult. A spontaneous break in the QRSs will helpful in recognizing the rhythm. 2:1 conduction with HR in 170s need not always cause hemodynamic instability because there is 2:1 conduction with apparent A-V synchrony  though only in every 2^nd P wave. But, this patient is slowly deteriorating. Therefore, treating this will be necessary – esp. in postoperative period.

Quiz #27 Answer: EKG with ST segment elevation

6 yr old boy, s/p Repair of subaortic membrane. Two EKGs with time are given – both recorded on the day of surgery. One is immediately after coming from OR and the other ~10 hrs later. Second EKG was performed due to EKG change in monitor. Hemodynamically stable. Patient is sleeping without any complaints.

1)      Describe the most significant change.

2)      What is the possible reason for the change?

Answers:

1)      St elevation in every lead except aVL and V1.

2)      Possible pericarditis – post-op.

Other possibilities:

1) Acute Myocardial Infarction

2) Hyperkalemia

3) Hypothermia

(All are discussed below in detail).

Patient Follow-up: No further investigations were done. Discharged home in 48 hrs. without any problems. Treated with Ibuprofen just like many other postop. cardiac patients. Followed by outside cardiologist.

Pericarditis: Characteristics of changes in Pericarditis: ST segment with concavity upwards and presence of this change in multiple leads favors diagnosis of pericarditis.

Ischemia or infarction changes will occur in specific areas that are affected (i.e. inferior leads, anterior leads, lateral leads, etc.) with reciprocal changes in “opposite” leads. Pericarditis typically involves ST elevation “all” leads and may not follow specific lead groups.

(Principles of Clinical Electrocardiography (11^th ed) by Mervin J. Goldman. Lange Medical Publications 1982, page 285).

AMI: Figure below shows acute EKG changes in inferior wall infarction in column B (Column A is normal EKG for comparison. Note the shape of ST segment (covexity upwards in II, III & aVF) and reciprocal changes in I, aVL, V1-V6).

(From Principles of Clinical Electrocardiography (11^th ed) by Mervin J. Goldman. Lange Medical Publications 1982, page 170)

Hyperkalemia: Hyperkalemia can present this way, but usually is associated with Tall peak T waves as well. Patient’s K in ABGs were normal. Below is an EKG strip from a newborn with Sr. K 9.1. The ST elevation and Tall T waves in hyperkalemia resemble AMI changes. But, these changes (at this Sr. K levels) will be interspersed with other EKG changes of QRS complex and arrhythmias as in this patient. (This baby was diagnosed with congenital adrenal hyperplasia later. Cardiology was consulted for bradycardia!)

Hypothermia: Occurs with characteristic appearance of Osborne waves (arrows). And, also occur with prolongation of QRS duration and QTc. Therefore, it is reasonable to do a 12-l2-lead EKG before instituting hypothermia protocol as an elective procedure (not possible when initiated during CPR).

(Image from internet)

Quiz 26: Clinical Sign

Questions:

1) Sulcus indicated by the dashed line in the chest of this infant is named after a physician. What name is it.

2)      Provide differential diagnoses for this clinical sign (including at least one relevant to cardiology).

Answers:

1) Harrison sulcus

2)      Diffierential diagnosis: (i) Rickets, (ii) Asthma and (iii) Congenital heart disease with significant L-R shunt. 

Discussion:
The line of indrawing approximately corresponds to insertion of diaphragm and is thought to be caused by repeated, forceful diaphragmatic pull during infancy when the bony cage is relatively soft. This occurs with any condition associated with chest retractions (Asthma & L-R shunt lesions in the heart). In rickets, normal pull of the diaphragm on the softer the bony cage (softer, due to rickets) is considered the reason.

Unnati sent this article on Harrison’s groove: Naish J & Wallis HRE. The significance of Harrison’s grooves. Br Med J 1948;1:541-44. This article has a discussion on mechanism of causation of this groove (or sulcus). It questions the theory of diaphragmatic pull in the early part. But, later part of the discussion provides evidence from work of Herlitz (1945) that supports this theory.

Quiz #25: Echo - Identify the vessel (again!)

Quiz #25:

Going with the same theme in Quiz #24.

Subcostal sagittal (bicaval) view in a newborn with severe cyanosis.

(Some labels are given because the picture is somewhat unclear. Clue: A vertical vessel flowing downwards, behind the IVC).

Question:

1)      Name the vessel shown by arrow.

2)      Provide a possible diagnosis. (I won’t be upset if you gave a second possible diagnosis as well!)

Answers:

1)      Vertical vein with flow from above downwards.

2)      Infradiaphragmatic type TAPVR

a.       Second possibility: SVC obstruction with decompression via Azygos vein (flowing downwards),

b.      Other possibilities (but, not typical) given by fellows who replied were

                                                               i.      Veno-venous collateral – I guess this may occur anywhere when there is a “set up” for it.

                                                             ii.      Scimitar syndrome – But, I think, the scimitar vein does not cross diaphragm as far as this image shows.

Quiz #24: Echo - Identify the vessel - Answer

Subcostal saggital view from a newborn with multiple congenital heart defects.

Questions:

1)      Name the vessel shown by the arrow.

2)      What is the possible reason for dilation of this vessel?

Answers:

1) Azygos vein

2) Dilated azygos vein, secondary to interrupted IVC.

Quiz #23 Answer: Shunt Calculcation (VSD with Eisenmenger)

Answers are in red fonts against the questions.

Scroll down for details of calculation.

Hypothetical case: 32 year old male with VSD and Eisenmenger syndrome. Necessary data are given.

Questions:

1)      What is the overall Qp/Qs?...1.0

2)      Calculate the effective pulmonary blood flow (Qep)….1.17 L/min/m²

3)      Calculate the amount of right to left shunt….0.35 L/min/m²

4)      Calculate the amount of left to right shunting….0.35 L/min/m²

(From Science and Practice of Pediatric Cardiology, 1990 ed. Page 921)

·         O2 content at 100% saturation is 17 g x 1.36 = 23.12 g%.

·         Qp:

=  (0.95 – 0.60) g% = 120/8.0 (x10 to convert to L/min/m2)

= 120/80 = 1.5 L/min/m².

·         Qs:

Qs = 120/23.1 (0.85-0.50) g% = 120/8.0*10 = 1.5 L/min/m².

Qp/Qs = 1.0

·         Effective PBF  (Qep):

Qep – 120/23.1(0.95-0.50) g% = 120/10.4 (x10 to convert to L/min/m²)

= 120/104 = 1.17 L/min/m².

(Both 1.15 and 1.17 are correct depending upon the calculation step at which you round the numbers. 1.15 is more correct than 1.17)!

·         R-L shunt:

(Qp – Qep) = 1.5 – 1.15 = 0.35 L/min/m²

(Pulmonary blood flow includes Qep + R-L shunt via VSD. Therefore, R-L shunt is Qp – Qep)

·         L-R shunt:

(Qs – Qep) = 1.5 – 1.15 = 0.35 L/min/m².

(Systemic blood flow includes Qep + L-R shunt via VSD. Therefore, L-R shunt is Qs – Qep).

Quiz #22: ICU monitor interpretation - Answers

5 month old baby. Postoperative day 1 after closure of membranous VSD. Panel 1 and Panel 2 were recorded few minutes apart.

(Click on the image to enlarge)

1.       What is the arrhythmia in Panel 1?

a.       JET (This patient already on Amiodarone. Therefore, JET rate is lower than usual)

2.       What type of pacing is done in Panel 2?

a.       Atrial pacing

3.       Describe the important difference between the CVP waveform in Panel 1 and Panel 2. What is the reason for the difference?

a.       “Giant” a-waves in Panel 1.

b.      Mechanism: Atrial contraction against closed AV valve. Junctional beat gets transmitted both atrium and ventricle. P wave is embedded inside the QRS. Both atria and ventricles contract at the same time, leading to atrial contraction against a closed AV valve (Ventricular contraction causes AV valves to close).

c.       Giant a-waves vs. Cannon a-waves: Strictly speaking, these two entities are different. In junctional rhythm, “Giant a-waves” are present in every beat. In contrast, “Cannon a-waves” are noted in complete AV block where P wave to QRS relationship is not 1 to 1. Some P wave happen to precede QRS. Therefore, some atrial contractions occur with AV valve open. Only occasional P waves conflict with QRS complexes causing atrial contraction with closed AV valve. Therefore, large a-waves are noted only in some beats…similar to a cannon firing only intermittent. Cannon needs to be packed with gun powder after each firing!

4.       Comment about AV conduction in Panel 2.

a.       Apparently, prolonged PR interval (First degree AV block). “Apparently” because actual measurements are not possible from these images.

5.       Why does arterial line trace have a “flat top”? How will you rectify this issue?

a.       Upper limit of the display-scale for arterial line is set at 90 mmHg. But, systolic BP is 99. This is rectified by either increasing the upper limit of display-scale or “auto adjust” mode on the monitor.

Quiz #21: EKG Answer

Question: What is the EKG diagnosis?

Answer: Wandering pacemaker

Discussion: Wandering pacemaker is characterized by 2-3 P wave morphologies and can be associated with variable PR interval (usually one PR interval length per P wave morphology). Rhythm will follow the background sinus rhythm.

In this patient, baseline rhythm is sinus arrhythmia. Each beat is a sinus beat (P, followed by QRS).

3 different P wave morphologies are noted (inverted, flat, and upright in rhythm strip - lead II). PR interval is 80 ms with inverted P wave and is ~120 ms with upright P wave.

This is not premature atrial contraction - because the complexes are not premature when a different P wave morphology appears!