Chamber dimensions

Ventricular wall thickness and mass

Figure 5.1 Parasternal long-axis echocardiogram demonstrating measurement of LV septal and posterior wall thickness and end diastolic diameter.

Figure 5.2 LV biometric data from normal (blue) and dilated cardiomyopathy (purple) hearts.

Athlete’s heart

It should be noted that highly trained athletes, particularly those competing in endurance sports, have cardiac measurements that fall outside the normal ranges quoted above. Studies suggest the majority of athletes’ measurements fall within the following values, although a small proportion of athletes have greater values, and exclusion of underlying heart disease must be determined.

Cardiac cycle

Time intervals (see Figure 5.3)

Figure 5.3 The normal cardiac cycle. (A) Schematic demonstrating the temporal relations of aortic pressure, left ventricular pressure, left atrial pressure, the phonocardiogram, the jugular venous pressure and the surface electrocardiogram during the cardiac cycle. (B) A schematic representation of left ventricular filling, ejection and isovolumic phases during the cardiac cycle.

The time intervals for the cardiac cycle are sensitive to heart rate. The following values are based upon a heart rate of 70 beats per minute:

Single complete cardiac cycle – duration ~ 0.9 s with HR = 70 bpm

Diastole:

• Isovolumic relaxation 0.08 s

• Ventricular filling 0.5 s

• Rapid passive filling 0.15 s

• Slow passive filling 0.22 s

• Atrial systole 0.13 s

• Isovolumic contraction 0.05 s

Systole:

• Ventricular ejection 0.3 s

Haemodynamics

Invasive measurements

Table 5.2 Intracardiac pressures

Figure 5.4 Schematic of the normal pressure tracings during cardiac catheterization of the right heart (above) and left heart (below).

Cardiac output calculations – Fick method

Figure 5.5 The Fick equation for calculation of cardiac output from arteriovenous oxygen gradient and VO₂.

Table 5.3 Normal ranges for cardiac output and resistance indices

Index	Normal range
Resting cardiac output (CO)	4–6 L/min
Cardiac index (CI)	2.5–4.0 L/min/m2
Stroke volume (SV)	75–105 ml
Stroke volume index (SVI)	40–70 ml/m2
Stroke work index (SWI)	40–80 g/m/m2
Pulmonary vascular resistance (PVR)	<200 dynes/s/cm−5 <2.5 Wood units

Systemic vascular resistance (SVR)

770–1500 dynes/s/cm⁻⁵

10–20 Wood units

Max LV dP/dt 1000–2400 mmHg/s

Pressure–volume analysis

Simultaneous pressure and volume recording using high-fidelity micromanometers and conductance catheters allows construction of pressure–volume loop relationships. These allow recording of PV relations during steady state and with dynamic manoeuvres such as preload or afterload alteration to provide load-independent measures of chamber function (see Figure 5.6).

Figure 5.6 A schematic diagram of the normal left ventricular pressure–volume relationship during steady state recording of one cardiac cycle (left) and during variation in preload or afterload to calculate load-independent parameters, e.g. the end systolic pressure–volume relationship (ESPVR).

Non-invasive measurements

Echo

Fractional shortening (FS) is a common measure of left ventricular cavity changes during the cardiac cycle when measured using M-mode echo:

Ejection fraction (EF) is the most common measurement used to report left ventricular function, and represents the % change in LV volume between systole and diastole. Simpson’s rule is used to calculate LV volume and EF from 2D measurements. It derives volume from a cubic relationship, assuming the LV cavity is ellipsoidal (see Figure 5.7):

Figure 5.7 Contrast echocardiography to measure left ventricular volumes and ejection fraction using Simpson’s rule from the apical 4-chamber view at end diastole (A) and end systole (B).

Diastolic function

Doppler assessment of the transmitral filling pattern is a measure of ventricular diastolic compliance. The transmitral filling pattern consists of two waves, E and A (see Figures 5.8 and 5.9). The E wave reflects passive filling during early (auxotonic) diastole, and the A wave is generated by atrial systole ejecting blood into the ventricle.

Figure 5.8 Schematic demonstrating normal and abnormal left ventricular diastolic physiology.

Figure 5.9 Doppler echocardiographic examples of transmitral left ventricular filling. A. Normal; B. Pseudonormal; C. E: A reversal; D. Restrictive.

The peak amplitude of the E and A waves, E wave deceleration time and the E:A ratio are measured to determine whether diastolic dysfunction is present. The E wave is usually greater than the A wave, but this varies with gender (see Table 5.5) and age (see Table 5.6). Peak E wave amplitude, E wave deceleration and the E:A ratio tend to fall with age in normal subject. This reflects the compliant younger ventricle, with 80–85% of diastolic filling occurring during the first two thirds of diastole. As the individual ages, atrial contraction contributes an increasing proportion of diastolic filling, with E and A waves peak velocities becoming equal (E:A ratio = 1) in the sixth or seventh decade.

Table 5.5 Normal transmitral Doppler flow indices and influence of gender

Parameter	Male	Female
Peak E wave (cm/s)	66 ± 15	70 ± 16
Peak A wave (cm/s)	67 ± 16	72 ± 18
E wave deceleration (s)	0.21 ± 0.04	0.19 ± 0.04
E:A ratio	1.04 ± 0.38	1.03 ± 0.34
E-at-A wave velocity (cm/s)	<20	<20

Table 5.6 Normal transmitral Doppler flow indices and influence of age

Left ventricular isovolumic relaxation time (IVRT)

PCWP estimation

Tei Index

Colour M-mode Doppler

Tissue Doppler

A normal spectral display recorded from the basal lateral left ventricular segment is presented in Figure 5.8.

E/E′ ratio is a measurement used to predict LA pressure. Normal range <10..

Left atrial parameters

Right atrial and right ventricular function

IVC collapse normally >50% with inspiratory effort if RA pressure <10 mmHg

Table 5.9 Right atrial pressure estimation using IVC collapse and hepatic vein flow

In vivo haemodynamic monitoring

Table 5.10 Intracardiac haemodynamic monitoring in patients with normal cardiac function

RVSP = right ventricular systolic pressure, RVDP = right ventricular diastolic pressure, estimated pulmonary artery diastolic pressure (ePAD) = RV pressure at point of PV opening = RV pressure at time of maximum +dPdt, +RV dPdt = maximum right ventricular dPdt.

Intrathoracic impedance monitoring

Normal threshold <60 Ω·d (76.9% sensitivity, 1.5 false positive results per patient year)

Radionuclide parameters of normal diastolic function

MVO₂ exercise testing

Exercise testing can be used to measure maximal/peak oxygen uptake (MVO₂) (ml/kg/min), which may be limited by cardiac output, peripheral perfusion, impaired skeletal muscle metabolism, impaired respiratory function, test compliance or other issues. If the individual achieves maximal aerobic capacity during exercise, and utilizes anaerobic metabolism for further ATP generation, then they have reached their anaerobic threshold. At the anaerobic threshold CO₂ generation exceeds O₂ utilization, and the respiratory quotient (CO₂ produced/O₂ uptake = RQ) >1.0.

Normal MVO₂ range is dependent upon age, sex, height and weight, with values below 25 ml/kg/min suggestive of possible cardiac impairment. Given the variability of normal range, reporting absolute MVO₂ has limitations, although in patients with severe heart failure, a peak MVO₂ of <14 ml/kg/min is an independent predictor of poor survival and a criteria for referral for cardiac transplantation.

Reporting MVO₂ as a percentage of predicted MVO₂ for the individual is more useful:

If MVO₂ <80% predicted and RQ >1.05 – cardiac limitation of exercise.

If MVO₂ <80% predicted and RQ <1.05 – non cardiac limitation of exercise e.g. check FEV1/FVC.

Ventilatory efficiency is also impaired in heart failure. This is calculated from the slope of minute ventilation (V_E) vs CO₂ production (VCO₂).

Serum natriuretic peptides

Two natriuretic peptides are available, brain natriuretic peptide (BNP) and N-terminal pro-brain natriuretic peptide (proNT-BNP).

Table 5.11 shows approximate normal and abnormal ranges for diagnosis of chronic heart failure in untreated patients, although these are sensitive to the assay and local laboratory values may vary. The sensitivity and specificity may also vary depending upon the value selected as upper limit of normal. The variation of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and extrapolated accuracy for BNP in the diagnosis of chronic heart failure are also presented in Table 5.11 (see also Table 5.12).

Dilated cardiomyopathy

The formal diagnosis requires the left ventricle to be dilated with the internal end-diastolic dimension (LVEDD) > 2.7 m² of body surface area and either ejection fraction < 45% or M-mode fractional shortening <30%. However, the normal distribution of ventricular dimension across the healthy population results in 1–2.5% of healthy individuals fitting either of these parameters (Figure 5.10).

Figure 5.10 Apical 4-chamber view of a dilated left ventricle with end diastolic (A) and end systolic (B) volumes calculated using planimetry and Simpson’s rule. (C) Parasternal short axis of a heart with dilated cardiomyopathy at end diastole.