2019

Question 1

Conclusions for the article “Echocardiographic phenotype of canine
dilated cardiomyopathy differs based on
diet type”

Answer 1

Dietary-associated DCM occurs with some GF diets and can improve with nutritional management, including diet change. The role of taurine supplementation, even without deficiency, is uncertain.

Question 2

Diferentials diagnosis for DCM phenotipe

Answer 2

can result from numerous etiologies including genetic mutations, infections, toxins, and nutritional
imbalances

Question 3

Echocardiographic phenotype of canine
dilated cardiomyopathy differs based on
diet type CONCLUSIONS

Answer 3

Dietary-associated DCM occurs with some GF diets and can improve with nutritional management, including diet change. The role of taurine supplementation, even without deficiency, is uncertain

Question 4

DCM predisposition

Answer 4

Dogs, male, large-breed dogs with certain breed predilections including Doberman Pinschers, Great Danes, and Irish Wolf- hounds

Question 5

The hallmark findings of DCM

Answer 5

Ventricular dilation and impaired contractility in the absence of primary valvular or vascular diseases

Question 6

Nutritional causes of DCM

Answer 6

Taurina and carnitina

Question 7

Nutrient toxicities associated with DCM

Answer 7

Iron and cobalt

Question 8

Conclusions: Association between atrial fibrillation and
right-sided manifestations of congestive
heart failure in dogs with degenerative
mitral valve disease or dilated
cardiomyopathy

Answer 8

Dogs with AF are more likely to manifest R-CHF than dogs without AF.
Cavitary effusions are an expected finding in approximately three-quarters of dogs
with AF and CHF secondary to either DCM or DMVD

Question 9

The strongest predictor of R-CHF

Answer 9

AF

Atrial fibrillation and right-sided congestive heart failure

Question 10

Conditions associated with R-CHF in the article “Atrial fibrillation and right-sided congestive heart failure”

Answer 10

The presence of AF, diagnosis of DCM, and moderate
to severe tricuspid regurgitation were associated with R-CHF in multivariate analysis
(Atrial fibrillation and right-sided congestive heart failure)

Question 11

The most common underlying

heart diseases associated with AF

Answer 11

dilated cardiomyopathy (DCM) and degenerative
mitral valve disease (DMVD). These diseases lead to both structural and electrical
remodeling of the atria that provide a profibrillatory substrate for initiation and propagation
of AF
(Atrial fibrillation and right-sided congestive heart failure)

Question 12

Hemodynamic consequences of AF

Answer 12

Decreased diastolic filling time and loss of
atrial contraction, both of which result in
decreased cardiac output and increased atrial
filling pressures. Because of these negative hemodynamic effects, onset of AF in patients
with underlying structural heart disease is often
accompanied by cardiac decompensation and
congestive heart failure (CHF).
(Atrial fibrillation and right-sided congestive heart failure)

Question 13

Proportions of dogs with AF that have CHF

Answer 13

63% - 100% of dogs with AF have concurrent
CHF
(Atrial fibrillation and right-sided congestive heart failure)

Question 14

What is predominant in the case of DCM? R or L CHF?

Answer 14

L-CHF

Atrial fibrillation and right-sided congestive heart failure

Question 15

Variables predictive of AF and R-CHF

Answer 15

The only variables that remained significantly associated with AF in multivariate analysis were heart rate and body weight
(Atrial fibrillation and right-sided congestive heart failure)

Question 16

variables were significantly associated with R-CHF in univariate logistic regression

Answer 16

Variables that remained significant in multivariate analysis were presence of AF, diagnosis of DCM, and moderate-to-severe TR
(Atrial fibrillation and right-sided congestive heart failure)

Question 17

DMVD dogs differed from DCM dogs in number of clinical and echocardiographic variables that reflect the distinct signalment and pathophysiology associated with each heart disease….

Answer 17

Compared with dogs with DMVD, dogs with
DCM were younger, larger, and more likely to be
male; had higher heart rates and more ventricular
arrhythmias; and demonstrated less dramatic LA
dilation.
(Atrial fibrillation and right-sided congestive heart failure)

Question 18

Why R-CHF is most frequently in case of AF than L_CHF?

Answer 18

a possible explanation for increased prevalence of
R-CHF in dogs with AF and left-sided structural
heart disease is that AF causes an acute increase in
RA pressure that is more hemodynamically significant than the pressure increase within an
already volume overloaded and dilated LA. It is theoretically possible that at
extremely high heart rates, LA pressure quickly
rises to critical levels; whereas at the more modest
tachycardia typical of AF (mean 218 beats per
minute in this study), the effects on RA pressure
are more clinically relevant.
(Atrial fibrillation and right-sided congestive heart failure)

Question 19

Clinical and echocardiographic variables predictive of AF

Answer 19

AF was more common in dogs with DCM than those with DMVD.
Within disease subgroups, dogs with AF had higher body weight than dogs without AF.
the only significant predictors
of AF in multivariate analysis were higher body
weight and higher heart rate. It is not surprising
that dogs with AF had higher heart rates than those
with underlying sinus rhythm, reflecting the
pathologically elevated heart rates associated
with this tachyarrhythmia.
(Atrial fibrillation and right-sided congestive heart failure)

Question 20

Conclusions: Anatomical anomalies and variations of
main thoracic vessels in dogs: a computed
tomography study

Answer 20

Major anatomical variations or anomalies of the main great thoracic
vessels in dogs without congenital cardiac disease were rare. An aberrant retroesophageal right subclavian artery was the most common anomaly found. Three slight
variations of common carotid artery branching were identified. These findings
might be of relevance for surgical or catheterization procedures.

Question 21

The main great thoracic vessels in dogs

Answer 21

ascending aorta, the aortic arch and the
descending aorta, the brachiocephalic trunk, subclavian arteries and veins, common carotid arteries, internal thoracic arteries and veins, axillary
artery and vein, superficial cervical artery and
vein, vertebral arteries and veins, the costocervical trunk, pulmonary arteries and veins, the
cranial vena cava and the post-hepatic caudal
vena cava and azygos veins

Question 22

Clasification of arterial and venous vascular anomalies

Answer 22

Sistemic, pulmonary or coronary

Question 23

the most important vascular

malformation in veterinary medicine

Answer 23

PDA

Question 24

Concept: Vascular

anomalies

Answer 24

Vascular anomalies are considered those that may be associated with clinical symptoms.

Question 25

Concept: anatomical variations

Answer 25

those alterations which do not lead to symptoms

Question 26

The most | frequently reported anatomical variations of the venous vasculature

Answer 26

the presence of a persistent | left cranial vena cava (PLCVC)

Question 27

The two configurations of left cranial vena cava | described in dogs

Answer 27

complete (where the PLCVC receives blood from veins cranial to the heart) or incomplete PLCVC (where the proximal portion of the PLCVC receives a vein which drains from the left costocervicalevertebral trunk)

Question 28

The technique for vascular evaluation

Answer 28

CT

Question 29

Description of the aberrant right subclavian artery

Answer 29

In all ARSA cases, the right subclavian artery branched directly from the aortic arch and passed dorsally to the oesophagus, forming an incomplete vascular ring around the oesophagus.

Question 30

Predisposition for ARSA

Answer 30

No association was identified between the presence of ARSA and sex, brachycephalic breed or weight groups

Question 31

Most comun Type of carotid artery branching

Answer 31

Type I

Question 32

Retro-oesophageal right subclavian | artery

Answer 32

An ARSA, the right subclavian artery arises directly from the aortic arch and passes dorsal to the oesophagus. This forms an incomplete vascular ring anomaly, where the oesophagus was mildly compressed between the vessel dorsally and the trachea ventrally, but it is not enough to cause clinical signs such as obstruction or dysphagia

Question 33

Dysphagia lusoria

Answer 33

Dysphagia secondary to extrinsic esophageal compression by an aberrant right subclavian artery

Question 34

Predisposition PLCVC

Answer 34

Shih Tzus and one Pekingese , and dogs under 10 kg and 5 kg

Question 35

There is association of carotid anatomy type and different breed morphotype (brachycephalic versus non-brachycephalic breeds) ?

Answer 35

No showed (Asymptomatic vascular anomalies in dogs)

Question 36

``` Conclusions: Quantitative assessment of two- and three-dimensional transthoracic and two-dimensional transesophageal echocardiography, computed tomography, and magnetic resonance imaging in normal canine hearts ```

Answer 36

Measurements of LV, RV, and RA volumes via 3D TTE and LA volume and LV EF assessed by CTA compared best with CMR. Three-dimensional echocardiography had lower interrater and intrarater CV compared with 2D TTE.

Question 37

``` Results: Quantitative assessment of two- and three-dimensional transthoracic and two-dimensional transesophageal echocardiography, computed tomography, and magnetic resonance imaging in normal canine hearts ```

Answer 37

No clinically relevant differences in LV volume were detected between CMR and all modalities. Importantly, 3D TTE had the lowest CV (6.45%), correlated with (rs ¼ 0.62, p ¼ 0.01), and had the highest overlap in distribution with CMR (OVL >80%). Left ventricular EF and LA size via CTA compared best with CMR and RV and RA volumes were best estimated by 3D TTE. Assessment of LV and LA volumes via 3D TTE had moderate repeatability (15e21%) compared with LV M-mode measurements and 2D LA-to-aortic ratio (<10%), respectively. For LV size, interrater CV for 3D TTE (19.4%) was lower than 2D TTE (23.1%).

Question 38

Number of specialized SAN conduction pathways that preferentially conduct electrical activation to atrial tissues

Answer 38

5

Question 39

Measure of the sino atrial node in dogs

Answer 39

11-29 mm long and 2-5 mm wide

Question 40

Intrinsic HR in the Sino Atrial Node in dogs

Answer 40

60-140 bpm

Question 41

Localization of the ‘leading pacemaker’ site, or the first site of SAN activation

Answer 41

the central part of the SAN

Question 42

Factors afected sino atrail node conduction

Answer 42

sympathetic and parasympathetic agonists, antiarrhythmic drugs, and naturally occurring metabolites including adenosine

Question 43

The most common rhythm disturbances that | require pacing to either alleviate clinical signs or prolong survival

Answer 43

Advanced second-degree and third-degree atrioventricular blocks, sick sinus syndrome, persistent atrial standstill, and vasovagal syncope

Question 44

the pathogen that most commonly | causes acute myocarditis and AVB in dogs

Answer 44

enteric coronavirus

Question 45

gold standard for in vivo diagnosis of myocarditis

Answer 45

Endoiocardial biopsie and increased serum concentrations of cTnI and cardiac troponin T are considered reliable to confirm the diagnosis

Question 46

Patogens described as cause of myocarditis in cats

Answer 46

Toxoplasma gondii , Bartonella henselae , Streptococcus canis , and Borrelia burgdorferi

Question 47

The occurrence of sudden cardiac | death among the population of dogs with AVB

Answer 47

42.7 %

Question 48

the occurrence of sudden death in dogs with second and third-degree AVB

Answer 48

40.6% and 32.8%, respectively. From the diagnosis, 24% of dogs die within 30 days and 40% of dogs die within six months

Question 49

association between age and sudden death

Answer 49

no demostrated in veterinary

Question 50

AVB and prognosis with drugs treatment

Answer 50

On the other hand, a negative association between terbutaline or methylxanthine administration (or both) and duration of survival has been reported

Question 51

alterations of the SA node in case of SSS

Answer 51

These changes include total or subtotal destruction of the SA node, areas of nodalatrial discontinuity, inflammatory or degenerative changes in the nerves and ganglias surrounding the SA node, and pathological changes in the atrial wall

Question 52

The molecular basis for some forms of congenital SSS

Answer 52

a recessive disorder of a human heart voltage-gated sodium channel

Question 53

Predisposition for dogs dogs | affected by SSS/SND

Answer 53

older, females are overrepresented, and Miniature schnauzers, West Highland white terriers, and Cocker spaniels are considered predisposed breeds

Question 54

The cardiopathologic findings observed in elderly dogs with myxomatous mitral valve disease in the sinus node (can predisposes to SSS)

Answer 54

significant changes, such as extensive damage of the SA node with depletion of the nodal cells and increase of fibrous or fibro-fatty tissue, interrupted contiguity between the SA node and the surrounding atrial myocardium, and interstitial fibrosis of the left and right atrial walls

Question 55

Prognosis in dogs with SSS and PM

Answer 55

In agreement with human medicine data, there is no evidence that cardiac pacing prolongs survival in dogs with sinus node disease. In one study, survival times did not differ between symptomatic and asymptomatic dogs or between dogs that received PM implantation and dogs that were medically treated (theophylline, propantheline, hyoscyamine, terbutaline)

Question 56

Cause of death in dogs with SSS

Answer 56

In dogs, the most common cause of death in the SSS population is euthanasia for non-cardiacerelated disease, even though several reported non-cardiacerelated causes could have been exacerbated by low cardiac output, causing poor peripheral perfusion

Question 57

Prognosis in case of SSS

Answer 57

The prognosis of SSS in dogs is usually good, although development of congestive heart failure does not appear to be mitigated by PM implantation

Question 58

Causes of perssitent atrial standstill

Answer 58

PAS has been described to occur in conjunction with a number of muscular dystrophy disorders and with amyloidosis and myocarditis . In dogs, although neuromuscular disease, long-standing cardiac disease, and myocarditis have been proposed as cause of PAS, this rhythm disturbance is generally attributed to atrial myopathy.

Question 59

Atrial myopathy

Answer 59

Atrial myopathy is characterized by progressive loss of atrial myocardium, with loss of the ability to conduct impulses, histological findings of myocardial necrosis, infiltration of inflammatory cells, and replacement fibrosis. Both the atrial myocardium and the conduction system are affected

Question 60

causes of temporary atrial standstill

Answer 60

can be secondary to digitalis toxicity, quinidine toxicity, myocardial infarction, hyperkalemia, hypoxia, and hypothermia

Question 61

Breeds predisposes to PAS

Answer 61

most commonly been reported in English springer spaniels and Labrador retrievers

Question 62

Prognosis in cases of PAs

Answer 62

It has been initially suggested that dogs with PAS have a poor prognosis, despite PM implantation. The median survival time of PAS dogs was reported to be approximately 28 months after pacing, indicating that these animals can be expected to survive a similar amount of time to dogs affects by other bradyarrhythmias . However, of the dogs with PAS that died, 64% suffered a cardiac-related death , which appears to be a relatively high incidence compared with other bradyarrhythmias, where it varies from 22% to 60% . Despite the high incidence of cardiac-related death in PAS dogs, no difference in survival times was noted between cardiac and noncardiac causes of death

Question 63

causes of intermittent symptomatic | bradyarrhythmias

Answer 63

intermittent/paroxysmal AVB, some forms of SND, such as tachycardiaebradycardia syndrome, and disturbance ofthe autonomic nervous system, such as vasovagal sinus arrest or AVB

Question 64

Clinical presentation of AVB

Answer 64

The most commonly reported clinical sign is transient loss of consciousness, which occurs in 23%e77% of dogs, followed by weakness and exercise intolerance (14%e 48%), lethargy (23%e26%), vomiting and diarrhea (11%e23%), and signs of congestive heart failure (3%e10%). In about 4% of cases, no clinical signs are reported. Congestive heart failure signs, such as ascites or pulmonary edema, can be present due to several myocardial changes induced during sustained abnormal AV activation and decreased heart rate

Question 65

third-degree AVB in cats

Answer 65

Clinical signs are present in the majority of cats with third-degree AVB, although around one-third of cats with third-degree AVB had their arrhythmia diagnosed as an incidental finding . If present, clinical signs are consistent with transient loss of consciousness or related to congestive heart failure.

Question 66

In Human in the case of 2º AVB, when it is assumed that the site of conduction failure is above the bifurcation of the bundle of His?

Answer 66

second-degree AVB with normal QRS duration, and it is | defined as type A.

Question 67

type B second-degree AVB

Answer 67

When there is a wide QRS complex and the site of block is assumed to be below the bundle branch bifurcation.

Question 68

When the second-degree AVB is named | advanced

Answer 68

When more than one P wave are block

Question 69

When we have a trifascicular block

Answer 69

Trifascicular block occurs when the right and left bundle branches are alternately interrupted due to infranodal disease or when a bifascicular block accompanies a nodal block with evidence of AV conduction disturbance

Question 70

Diagnosis of persistent atrail standstil

Answer 70

Electrocardiographic findings of PAS are absent P waves and idioventricular escape rhythm with normal serum potassium concentration

Question 71

survival times after PM implantation in case of PAS

Answer 71

it appears that dogs with PAS have similar survival | times than in cases of other bradiarrhythmias

Question 72

In human, contraindication for singlechamber atrial pacing

Answer 72

A Wenckebach point of <120 beats per minute in | humans is considered a contraindication for singlechamber atrial pacing

Question 73

contraindications to physiologic VDD PMs

Answer 73

dogs that present an atrial rate <70 beats per minute and a negative atropine response test (<25% increase of sinus rate 20e30 min post 0.04 mg/kg atropine SQ injection). Other contraindications to physiologic VDD PMs are represented by AVB complicated by AF or supraventricular tachycardia.

Question 74

statistically significant benefit in survival times in dogs that received a physiologic VDD PM compared with dogs that received a nonphysiologic VVI PM

Answer 74

recent retrospective study demonstrated no statistically significant benefit in survival times in dogs that received a physiologic VDD PM compared with dogs that received a nonphysiologic VVI PM

Question 75

PM. Pacing thresholds

Answer 75

Pacing thresholds have been shown to be lower in the acute setting, and chronic pacing thresholds typically rise over time.

Question 76

The conductor wires are an alloy of

Answer 76

nickel, cobalt, chromium, and molybdenum. MP-35N (SPS | Technologies, Cleveland)

Question 77

Hoe appeared abrasion the abrasion of the insulation material, exposing the conductors, and cause lead failure

Answer 77

with a low lead impedance measurement | (short circuit) during pacemaker interrogation

Question 78

Electrode tips materials

Answer 78

```   Platinum iridium   Elgiloy e cobalt, iron, chromium, molybdenum, nickel, and manganese   Platinized platinum e platinum coated with platinized titanium   Vitreous or pyrolytic carbon   Titanium   Titanium oxide   Iridium oxideecoated titanium   Titanium nitride ```

Question 79

The design of actual pacemakers

Answer 79

incorporates a sensing circuit, a logic circuit, and an output circuit, with the ability to communicate with a pacemaker programmer and a remote-monitoring device

Question 80

The output circuit of the pacemaker

Answer 80

consists of two basic factors: voltage and duration. The former is the programmed voltage, and the latter is the pulse width of the delivered pacing pulse.

Question 81

The | largest component of the output circuit in the PM

Answer 81

The battery

Question 82

The battery longevity can roughly be calculated

Answer 82

``` Usable battery capacity   1.2 amp hours. Pacer current drain   20 microamps. Hours in 1 year   8760. [1,200,000 microamps (hrs)]/20 microamps   60,000 h. 60,000 h/8760   6.849 years. The energy delivered plays a significant role in longevity. The energy equation is (E   V2   t)/R. where V   output voltage, t   pulse width of pacing pulse, and R   resistance. The energy (E) delivered is expressed in micro Joules. ```

Question 83

Some PM devices begin to turn off certain | functions when appeared the replacement indicator or elective replacement time

Answer 83

rate response and automatic threshold | testing

Question 84

Historically, non-MRI conditional | devices would be contraindicated for scanning.

Answer 84

However, several studies have shown that patients with these devices can safely have an MRI (non-thoracic) at 1.5 T

Question 85

Devices are typically labeled as Magnetic resonance imaging (MRI) compatible, conditional, or non-MRI conditional.

Answer 85

Devices labeled as compatible are safe for whole-body scans without regard to the patient positioning. Devices labeled as conditional are safe for scans with proper programming and generally not for scanning the implant area. Typically, the recommendation is for scans at 1.5 T or less.

Question 86

leads problems

Answer 86

conductor wires can break, and insulation can degrade, exposing the conductors. Tying down the suture sleeve on the lead too tight can cause a crush phenomenon, damaging the conductor wires and causing the lead to fail.

Question 87

sutures used for securing the lead wires to the | fascia

Answer 87

are non-absorbable 2-0 Ticron or 2-0 Silk

Question 88

Consequences of damaging the insulation at the implant

Answer 88

it can expose the conductor wire, causing a short circuit. This results in very low impedance values and can cause rapid battery depletion because of a damaged lead.

Question 89

Consecuences of not tightening the setscrew enough

Answer 89

will cause high impedance (open circuit) and loss | of pacing

Question 90

External defibrillation in the case of PM

Answer 90

External defibrillation is generally safe, and the pads (or paddles) should be placed as far away from the device as possible but still give a good vector for defibrillation. Energy from the external defibrillator can be coupled into the device, causing major component failure. Sometimes, this results in a reset (or backup) mode within the pacemaker which can generally be reset with the programmer, and other times, it can be a terminal condition resulting in no output.

Question 91

Pacemaker parameters

Answer 91

Setting of output parameters (pulse amplitude and pulse width)   Sensitivity parameter settings   Impedance (component and system including patient interface)

Question 92

Ohm’s law

Answer 92

V  = IR.where V   the voltage or the force which drives the current I   the current, described as the flow of electrons past a certain point measured in milliamperes R   the resistance (impedance) or opposition to flow of electrical current expressed in Ohms (U).

Question 93

Relationship between impedance and current

Answer 93

Impedance and current have an inverse relationship.

Question 94

Resistance versus impedance

Answer 94

Resistance and impedance are both expressed in Ohms; however, the two differ in that resistance is the opposition to current flow in a direct current circuit, whereas impedance describes the resistance to current flow in an alternating current circuit. The terms are often used interchangeably when describing current flow in pacing circuits

Question 95

Range of normal impedance values

Answer 95

Impedance values typically range from 300 to | 1200 U.

Question 96

Impedance of <200 U

Answer 96

A low impedance measurement (<200 U) indicates | a short circuit, usually from an insulation breach.

Question 97

Impedance >2000 U

Answer 97

An unusually high impedance measurement (>2,000 U) indicates an open circuit, typically caused by a conductor fracture.

Question 98

The capture threshold

Answer 98

``` is the minimum amount of energy delivered by the device to consistently depolarize (capture) the myocardium. ```

Question 99

The capture threshold increased or decreased with the time

Answer 99

Thresholds are typically low at the initial implant and generally rise over time as the leads become chronic [18]. Typically, the output voltage to the lead(s) can be decreased to twice the pacing threshold 90 days after implant. At this point, the leads are generally considered to be chronic.

Question 100

Acceptable pacing thresholds for canines

Answer 100

Acceptable pacing thresholds for canines are <1.5 V for an acute implant and <2.5 V for a chronically implanted system.

Question 101

the capture safety margin or | threshold safety margin

Answer 101

A generally accepted tenet is that the device should be programmed to twice the pacing threshold.

Question 102

Loss of capture

Answer 102

Loss of capture occurs when the output pulse from the pacemaker is of insufficient amplitude to capture the heart (loss of capture)

Question 103

the output parameters

Answer 103

pulse amplitude and pulse width

Question 104

The strength-duration curve

Answer 104

The strength-duration curve is particularly useful because the chronaxie shows the combination of pulse width and pulse amplitude (voltage and duration) that uses the least energy to reliably capture the heart.

Question 105

Rheobase

Answer 105

The lowest voltage threshold at an infinitely wide pulse width

Question 106

Chronaxie Point

Answer 106

The width point a twice the rheobase

Question 107

Sensing (PM)

Answer 107

Sensing refers to the capability of the device to | detect intrinsic cardiac activity

Question 108

Unipolar sensing

Answer 108

Unipolar sensing refers to the use of the pacemaker itself and the tip of the pacing lead as the antenna for sensing. This results in a larger signal and is more likely to sense myopotentials and could possibly cause oversensing. The possibility of pacemaker inhibition to the sensing of extraneous signals is more likely in a unipolar sensing circuit.

Question 109

bipolar sensing circuit

Answer 109

A bipolar sensing circuit uses a much smaller antenna than the unipolar because the anode and cathode are incorporated into pacing lead and is less likely to oversense extraneous signals. The height, or amplitude, of the smaller signal is then amplified and measured by the device.

Question 110

Sensing program in the PM

Answer 110

An acceptable intrinsicmeasured atrial signal is>1mV, whereas an acceptable measured ventricular signal would be>10mVfor the typical canine implant. The typical safety margin is 2:1. For example, an atrial signal of 1 mV would require the atrial sensitivity to be programmed to .5 mV. In contrast to the pacing threshold which is two times the capture thresholds, the sensing circuit is just the opposite. A smaller value is programmed to make the device more sensitive. In this case, the sensitivity should be programmed to at least themeasured intrinsic signal.

Question 111

Pacing modes. Chamber I

Answer 111

It indicates the chamber (or chambers) paced. If only one chamber is paced, the designation would be either A or V, and if both chambers are paced, the designation would be D. O indicates that no chamber is paced. A manufacturer code of ‘S’ in this position indicates single chamber is paced (atrial or ventricular).

Question 112

Pacing modes. Chamber II

Answer 112

Position II indicates the chamber (or chambers) sensed. If only one chamber is sensed, the designation would be A or V, and if both chambers are sensed, the designation would be D. O indicates that no chamber is sensed. A manufacturer code of ‘S’ in this position indicates that single chamber is sensed (atrial or ventricular).

Question 113

Pacing modes. Chamber III

Answer 113

Position III indicates the mode of response to sensing. Triggered means the device will pace when an intrinsic signal is sensed. Inhibit means the pacing output will be withheld when an intrinsic signal is sensed. D indicates that the device can both trigger and inhibit in response to intrinsic signals. O indicates that there is no response (neither triggered nor inhibited) to sensed intrinsic signals. Essentially, this is committed pacing.

Question 114

Pacing modes. Chamber IV

Answer 114

Position IV indicates other programmable functions of the device. Rate modulation allows the device to change its pacing rate based on physiologic need such as increased activity. Communicating indicates that the device can transmit and receive information regarding diagnostics or programming. Multiprogrammable means that greater than three parameters are programmable. All pacemakers today are multiprogrammable. P indicates simple programmable, limiting the functions to three or less. It would be rare to see any of these types of devices in operation today.

Question 115

Pacing modes. Chamber V

Answer 115

Position V is reserved for antitachycardia functions. This would indicate that the device can rapidly pace a tachycardic rhythm, shock a tachycardic rhythm, or both. Most cardiac defibrillators utilize the ‘D’ designation in this position.

Question 116

How work Dual chamber systems

Answer 116

Dual chamber systems with a single lead that allows for atrial synchronous ventricular-inhibited pacing use one pacing lead that incorporates both a pacing electrode within the right ventricle and a floating atrial electrode within the intra-atrial portion of the ventricular lead to sense P waves propagated through the blood. These native P waves are sensed by the pacemaker, and then after an appropriately programmed atrioventricular delay, the system delivers a ventricular pacing impulse.

Question 117

Testing the pacemaker lead

Answer 117

These parameters include sensed P wave amplitude (if implanting an RA lead), sensed R wave amplitude (for ventricular leads), current of injury, lead impedance, and threshold testing.

Question 118

Sense P wave

Answer 118

In our experience, most leads within the right auricular appendage or RA septum sense P waves that are between 3 and 3.5 mV.

Question 119

Sense R wave

Answer 119

Generally, an appropriately placed RVA pacing lead will measure/sense an R wave that is at least 10 mV (and usually higher). With RV septal/groove placement of leads, the R wave amplitude will be much smaller than that with RVA leads. Acceptable R wave amplitude in these locations is 4e5 mV because of the perpendicular alignment of the dipoles and also because there is less muscle and vector in this plane.

Question 120

LV leads sensing

Answer 120

LV leads will generally sense larger amplitude R waves than RVA leads. In our population of dogs with implanted LV leads that were stable long term, we have seen R wave amplitudes of 15e20 mV

Question 121

ST segment elevation on the intracardiac | electrogram during PM implantation

Answer 121

Both passive- and active-fixation leads are initially traumatic to the myocardium when implanted and can temporarily cause increased pacing threshold. The magnitude of this current of injury can be assessed with a PSA and is characterized as prolongation of the atrial or ventricular depolarization and ST segment elevation on the intracardiac electrogram

Question 122

The current of injury

Answer 122

The current of injury indicated by an increase in the duration of the intracardiac electrogram (msec) and the magnitude of ST segment elevation (mV) can be used to assess the adequacy of active-fixation at the time of lead implantation.