CATH HEMODYNAMICS

Presenter – Dr Virbhan BalaiModerator –Y.K Arora

Cardiac cycle • The first stage, " diastole," is when the semilunar valves (the pulmonary

valve and the aortic valve) close, theatrioventricular (AV) valves (the mitral valve and the tricuspid valve) open, and the whole heart is relaxed.

• The second stage, "atrial systole," is when the atrium contracts, and blood flows from atrium to the ventricle.

• The third stage, "isovolumic contraction" is when the ventricles begin to contract, the AV and semilunar valves close, and there is no change in volume.

• The fourth stage, "ventricular ejection," is when the ventricles are contracting and emptying, and the semilunar valves are open.

• During the fifth stage, "isovolumic relaxation time", pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta.

HEMODYNAMIC DATA

The hemodynamic component of the cardiac catheterization procedure- Pressure measurements Measurement of flow (e.g., cardiac output, shunt

flow, flow across a stenotic orifice, regurgitant flow, and coronary blood flow)

Determination of vascular resistance.

Pressure Measurement Systems

• Fluid-Filled Systems. Intravascular pressure is typically measured with the use of a fluid-filled catheter attached to a pressure transducer.

• The pressure wave is transmitted from the tip of the catheter to the transducer by the fluid column within the catheter.

• Most pressure transducers are disposable electrical strain gauges. The pressure wave distorts the diaphragm or wire within the transducer. This energy

The pressure transducer must be calibrated against a known pressure, and establishment of a zero reference must be undertaken at the start of the catheterization procedure.

To “zero” the transducer, the transducer is placed at the level of the atria, which is approximately midchest.

Micromanometer Catheters. Commercially available high-fidelity micromanometer systems have both an end hole and side holes to allow over-the-wire insertion into the circulation while also permitting angiography.

Catheters that have two transducers separated by a short distance are useful for accurate measurement of gradients across valvular structures and within ventricular chambers.

Normal Pressure Waveforms

Atrial Pressure

The right atrial pressure waveform has three positive deflections, the a, c, and v waves.

The a wave is due to atrial systole and follows the P wave on the ECG.

The height of the a wave depends on atrial contractility and resistance to RV filling.

The x descent fo- represents relaxation of the atrium and downward pulling of the tricuspid annulus by RV contraction.

The x descent is interrupted by the c wave, which is a small positive deflection caused by protrusion of the closed tricuspid valve into the right atrium.

The v wave - represents RV systole. The y descent occurs after the v wave and

reflects opening of the tricuspid valve and emptying of the right atrium into the right ventricle.

Normal Pressure

Normal right- and left-sided heart pressures

Ventricular Pressure

RV and LV waveforms are similar in morphology. They differ mainly with respect to their magnitudes. The durations of systole and isovolumic contraction

and relaxation are longer and the ejection period is shorter in the left than in the right ventricle.

There may be a small (5 mm Hg) systolic gradient between the right ventricle and pulmonary artery.

Pathologic Waveforms

Cardiac Output Measurements

• Thermodilution • Fick methods.

Fick Method. The Fick principle estimates cardiac output by using the assumption that pulmonary blood flow (PBF) is equal to systemic blood flow (SBF) in the absence of an intracardiac shunt.

Thermodilution cardiac output curves

Fick cardiac output (liters/) min= Oxygen consumption (mL/ min) A-V02 x1.36xHgb x10 Where A-VO2 is the arterial-venous oxygen

saturation difference, Hgb is the hemoglobin concentration (mg/dL), and the constant 1.36 is the oxygen-carrying capacity of hemoglobin (expressed in mL O2/g Hgb).

Angiographic Cardiac Output

Angiographic cardiac output and stroke volume are derived from the following equations:

Stroke volume =EDV -ESV Cardiac output = EDV- ESV Heart rate

Determination of Vascular Resistance.

• Total pulmonary resistance (TPR): • TPR = 80(PAm ) Qp

Evaluation of Valvular Stenosis

Determination of Pressure Gradients Aortic Stenosis Transvalvular pressure gradient is best

measured with a micromanometer catheter and simultaneous recordings in the left ventricle and supravalvular aorta.

A dual-lumen pigtail catheter is the most commonly used and preferred catheter.

GENERAL PRINCIPALE

Intermittent frequent flushing of the lumen with heparinized saline

Femoral artery pressures should not be used to measure the aortic valve gradient because peripheral amplification may cause a false decrease in gradient.

Catheters with side holes should be used because damping can occur with an end-hole catheter.

The peak-to-peak gradient measured in the catheterization laboratory is generally lower than the peak instantaneous gradient measured in the echocardiography laboratory.

Patients with fixed obstruction (either valvular stenosis or fixed subvalvular stenosis) will demonstrate a parvus and a tardus in the upstroke of the aortic pressure, Right, The left ventricular pressure also has a late peak because of the mechanism of this dynamic obstruction. LA indicates left atrium.

Mitral Stenosis

The most accurate means of determining the mitral valve gradient is direct measurement of left atrial pressure by the transseptal technique with simultaneous measurement of LV pressure.

Pulmonary capillary wedge pressure is usually substituted for left atrial pressure because it is more readily obtained.

Pulmonary wedge pressure may systematically overestimate left atrial pressure by 2 to 3 mm Hg, thereby increasing the measured mitral valve gradient.

Improperly wedged catheters resulting in damped pulmonary artery pressure recordings further overestimate the severity of mitral stenosis.

If accurate positioning of the catheter in the wedge position is in doubt, the position can be confirmed by slow withdrawal of blood for oximetric analysis.

Oxygen saturation equal to that in the systemic circulation confirms the wedge position.

Optimally performed with a large-bore end-hole catheter. measurement. Right, small-lumen thermodilution catheter. damped pulmonary artery pressure.

The gradient using a pulmonary artery wedge pressure will frequently overestimate the true transmitral gradient.

Right-Sided Valvular Stenosis

In pulmonic stenosis, the valve gradient is obtained by catheter pull-back from the pulmonary artery to the right ventricle or by placement of separate catheters in the right ventricle and pulmonary artery.

Multi lumen catheters can also be used for simultaneous pressure recordings.

Tricuspid valve gradients should be assessed with simultaneous recording of right atrial and RV pressure.

Left, In this patient with restrictive cardiomyopathy, there is a drop in left ventricular pressure and a drop in right ventricular pressure during inspiration (Insp). Right, In this patient with constrictive pericarditis, there is ventricular discordance, with an increase in right ventricular pressure and a decrease in left ventricular pressure during inspiration.

Calculation of Stenotic Valve Orifice Areas

Flow (F) and orifice area (A) are related by the fundamental formula F=cAV Hence, A= F/cV =

The maximal discrepancy between the actual mitral valve area and calculated values was just 0.2 cm2 when the constant 0.85 was used.

No data were obtained for aortic valves, a limitation noted by the Gorlins, and a constant of 1.0 was assumed.

Assessment of Valvular Regurgitation According to ACC/AHA guidelines,

hemodynamic evaluation of either aortic or mitral regurgitant lesions is recommended as a class I indication when pulmonary artery pressure is disproportionate.

Visual Assessment of Regurgitation

Valvular regurgitation may be assessed visually by determination of the relative amount of radiographic contrast medium that opacifies the chamber proximal to its injection.

Estimation of regurgitation depends on the volume of regurgitant, as well as on the size and contractility of the proximal chamber.

Sellers and colleagues

Regurgitant Fraction

A gross estimate of the degree of valvular regurgitation may be obtained by determination of the regurgitant fraction (RF).

The difference between angiographic stroke volume and forward stroke volume can be defined as the regurgitant stroke volume.

Regurgitant stroke volume =Angiographic stroke volume - Forwa rd stroke volume

The RF is the portion of the angiographic stroke volume that does not contribute to net cardiac output.

When compared with visual interpretation, 1+ regurgitation is roughly equivalent to an RF of 20% or less, 2+ to an RF of 21% to 40%, 3+ to an RF of 41% to 60%, and 4+ to an RF of greater than 60%.

Shunt Determinations

Normally, PBF and SBF are equal. Unexplained pulmonary artery oxygen saturation exceeding 80%

should raise suspicion for a left-to-right shunt, Unexplained arterial desaturation (<93%) may indicate a right-to-left

shunt. Arterial desaturation commonly results from alveolar hypoventilation

and associated “physiologic shunting,” causes of which include oversedation from premedication, pulmonary disease, pulmonary venous congestion, pulmonary edema, and cardiogenic shock.

If arterial desaturation persists after the patient takes several deep breaths or after administration of 100% oxygen, a right-to-left shunt is likely.

Oximetric Method

The oximetric method is based on blood sampling from various cardiac chambers for determination of oxygen saturation.

If the difference in oxygen saturation between these samples is 8% or greater, a left-to-right shunt may be present.

Oxygen saturation in the IVC is higher than in the SVC because the kidneys have lower oxygen extraction relative to their blood flow than other organs do.

A full saturation run obtains samples from the high and low IVC; high and low SVC; high, middle, and low right atrium; RV inflow and outflow tracts and midcavity; main pulmonary artery; left or right pulmonary artery; pulmonary vein and left atrium, if possible; left ventricle; and distal aorta.

Shunt Quantification

If a pulmonary vein is not sampled, systemic arterial oxygen saturation may be substituted, assuming that it is 95% or greater.

If systemic arterial saturation is less than 93%, a right-to-left shunt may be present.

If arterial desaturation is present but not secondary to a right-to-left shunt, systemic arterial oxygen content is used.

If a right-to-left shunt is present, pulmonary venous oxygen content is calculated as 98% of the oxygen capacity.

A ratio of less than 1.5 indicates a small left-to-right shunt.

A ratio of 1.5 to 2.0, a moderate-sized shunt. A ratio of 2.0 or higher indicates a large left-

to-right shunt. A flow ratio of less than 1.0 indicates a net

right-to-left shunt.

Pharmacologic Maneuvers

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