Sinus tachycardia is seen in many patients with pulmonary embolism. New right bundle branch block (RBBB) or right axis deviation with "strain" can also indicate PE. The classic SIQIIITIII is less common.

Zoom lens are used for instances where you want to fill the frame with a subject that is far in distance and you wish it to appear much closer. Good examples would be sports or animal photography where you cannot be physically close to the subject. Or maybe it is possible but you’d rather not disturb the subject, choosing instead to photograph it naturally. This is particularly useful for street photography where you don’t want the person to know they are being photographed until after the shot is taken.

The limb leads look at the heart in a vertical plane (see Figure 2), whereas the chest leads look at the heart in a horizontal plane. In this way, a three-dimensional electrical picture of the heart is built up (see Table 1).

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The ST segment, which is also known as the ST interval, is the time between the end of the QRS complex and the start of the T wave. It reflects the period of zero potential between ventricular depolarization and repolarization.

In a normal ECG, T waves are upright in every lead except aVR. T-wave inversion can represent current ischemia or previous infarction (see Figure 17). In combination with LVH and ST depression, it can represent "strain". This form of LVH carries a poor prognosis.

A normal focal length is known to be 50mm. When you shoot with a lens set at 50mm focal length, the subject will be photographed in size as you saw it in real life. If you zoom your lens out to 100mm focal length, the image will now be magnified X 2 so the subject appears much closer. Therefore the definition of a telephoto zoom lens is one that can be magnified higher than 50mm focal length.

P waves are the key to determining whether a patient is in sinus rhythm or not. If P waves are not clearly visible in the chest leads, look for them in the other leads. The presence of P waves immediately before every QRS complex indicates sinus rhythm. If there are no P waves, note whether the QRS complexes are wide or narrow, regular or irregular.

Why is this important to know? There has been many instances where I’ll be trying to photograph a subject that is only a few meters from me and the lens keeps swimming in and out, not able to focus. I’ve fixed this problem every time by setting the correct metering. ie I set 1.8m -∞ for subjects closer than 6.5 meters away, and set 6.5m-∞ for everything 6.5 meters or further in distance.

Three bipolar leads and three unipolar leads are obtained from three electrodes attached to the left arm, the right arm, and the left leg, respectively. (An electrode is also attached to the right leg, but this is an earth electrode.) The bipolar limb leads reflect the potential difference between two of the three limb electrodes:

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Long telephoto zoom lenses are perfect for photographing macro subjects. They allow you to stand further away from the subject so not to scare it away. This has its obvious advantages when shooting timid subjects like dragonflies and insects.

A reverse tick ST depression is characteristic and does not indicate toxicity. Digoxin toxicity can result in dysrhythmia.

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Long QT syndrome may also be drug-induced (see Table 4, p. 32). Once this occurs, the responsible drug needs to be discontinued.

Nobody knows for sure why these letters became standard. Certainly, mathematicians used to start lettering systems from the middle of the alphabet to avoid confusion with the frequently used letters at the beginning. Einthoven used the letters O to X to mark the timeline on his ECG diagrams and, of course, P is the letter that follows O. If the image of the PQRST diagram was striking enough to be adopted by researchers as a true representation of the underlying form, it would have been logical to continue the same naming convention when the more advanced string galvanometer started creating ECGs a few years later.

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The standard ECG uses 10 cables to obtain 12 electrical views of the heart. The different views reflect the angles at which electrodes "look" at the heart and the direction of the heart's electrical depolarization.

find the QRS complex in the I and aVF leads (because these look at the heart at 0° and +90°, respectively)determine the net positivity of the QRS wave from each of the two leads by subtracting the S wave height (the number of small squares that it crosses as it dips below the baseline – if it does) from the R wave height (the number of small squares that it crosses as it rises) (see Figure 9a and 9b)plot out the net sizes of these QRS waves against each other on a vector diagram (see Figure 9c). For the I lead, plot net positives to the right and net negatives to the left; for the aVF lead, plot positive downwards and negative upwardsthe direction of the endpoint from the starting point represents the axis or predominant direction of electrical depolarization (determined primarily by the muscle mass of the left ventricle). It is expressed as an angle and can be estimated quite easily (normal is 0°–120°)

The three waves of the QRS complex represent ventricular depolarization. For the inexperienced, one of the most confusing aspects of ECG reading is the labeling of these waves. The rule is: if the wave immediately after the P wave is an upward deflection, it is an R wave; if it is a downward deflection, it is a Q wave:

A distance of more than five small squares from the start of the P wave to the start of the R wave (or Q wave if there is one) constitutes first-degree heart block (see Figure 10). It rarely requires action, but in the presence of other abnormalities might be a sign of hyperkalemia, digoxin toxicity, or cardiomyopathy.

A telephoto zoom lens is my favorite piece of glass. Over the years I’ve photographed with Canon, Nikon and Sigma telephoto zoom lens. Before we let you in on the secrets of using these long lenses, we’ll first discuss a couple of basics.

The route that the depolarization wave takes across the heart is outlined in Figure 3. The sinoatrial node (SAN) is the heart's pacemaker. From the SAN, the wave of depolarization spreads across the atria to the atrioventricular node (AVN). The impulse is delayed briefly at the AVN and atrial contraction is completed.

Identify the QRS complex (this is generally the biggest wave); count the number of large squares between one QRS wave and the next; divide 300 by this number to determine the rate (see Table 2).

The focus limit switch tells the camera where to focus within certain ranges in distance. For example, if you set the switch to 6.5m-∞ then the camera knows not to worry about focussing on anything closer than 6.5 meters. Knowing this information, your camera will shoot faster.

Just because it’s a long lens doesn’t mean you need to use a tripod. In fact I rarely use a tripod when using my telephoto lens. I find them too restrictive when photographing birds and wildlife.

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The unipolar leads reflect the potential difference between one of the three limb electrodes and an estimate of zero potential – derived from the remaining two limb electrodes. These leads are known as augmented leads. The augmented leads and their respective limb electrodes are:

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Using a telephoto zoom lens will totally change the overall feel of the image. Especially when photographing subjects that are further in distance from you. Not only does it bring the main subject closer, but it also brings all the background elements closer as well.

The wave of depolarization then proceeds rapidly to the bundle of His where it splits into two pathways and travels along the right and left bundle branches. The impulse travels the length of the bundles along the interventricular septum to the base of the heart, where the bundles divide into the Purkinje system. From here, the wave of depolarization is distributed to the ventricular walls and initiates ventricular contraction.

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The ST segment extends from the end of the S wave to the start of the T wave. It should be flat or slightly upsloping and level with the baseline. Elevation of more than two small squares in the chest leads or one small square in the limb leads, combined with a characteristic history, indicates the possibility of MI (see Figure 15, previous page). ST depression is diagnostic of ischemia (see Figure 16). It is worth noting that although ST elevation can localize the lesion (eg, anterior MI, inferior MI), ST depression cannot. Concave upwards ST elevation in all 12 leads is diagnostic of pericarditis.

The axis is the net direction of electrical activity during depolarization. It is altered by left ventricular or right ventricular hypertrophy or by bundle branch blocks. It is a very straightforward measurement that, once it has been grasped, can be calculated instantaneously:

There is some debate over exactly who invented the electrocardiogram. The Dutch "K" (elektrokardiogram) is often used as a tribute to the Indonesian-born physician Wilhelm Einthoven who, while working in The Netherlands in 1924, received the Nobel prize for "the discovery of the mechanism of the electrocardiogram". In fact, it was Augustus Désiré Waller, a physician trained in Edinburgh, who presented – to the students of St Mary's Hospital medical school, London, at the introductory lecture of the 1888 academic year – his "cardiograph", the first ever ECG recording in man. It was some years later, in 1901, that Wilhelm Einthoven reported his string galvanometer – with the limb leads labeled I, II, and III and the waves labeled P, QRS, and T as we know them today. In fact, although often credited with inventing the term electrocardiogram (which is why it is sometimes spelt the Dutch way), Einthoven credits Waller with this distinction in his 1895 publication in Pflügers Archives "Über die Form des menschlichen Elektrokardiogramms".

The ECG machine processes the signals picked up from the skin by electrodes and produces a graphic representation of the electrical activity of the patient's heart. The basic pattern of the ECG is logical:

British physiologist Augustus D Waller of St Mary's Medical School, London, published the first human electrocardiogram in the British Medical Journal in 1888. It was recorded from Thomas Goswell, a technician in the laboratory, using a capillary electrometer. After that, Waller used a more available subject for his demonstrations – his dog Jimmy, who would patiently stand with his paws in glass jars of saline.

All lenses require different techniques for photographers to grasp. Just because you know how to use one lens doesn’t mean you can use the same technique on the next. As strange as it sounds, telephoto and macro lenses have a lot in common. Personally I treat them much the same way.

The cardiac depolarization route. AVN: atrioventricular node; SAN: sinoatrial node. Reproduced with permission from WB Saunders (Guyton A, Hall J. Textbook of Medical Physiology. Philadelphia: WB Saunders, 1996).

A sinus-wave QRS should be treated immediately with calcium chloride, whilst hyperkalemia associated with lesser ECG changes can be treated with insulin/glucose infusion.

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The first time I used my Canon EF 70-200mm f/4L USM lens on a tripod, was to photograph beautiful night shots of the Opera House in Sydney. Looking at the images on my computer I saw they were all out of focus and appeared to have symptoms of camera shake. I later found that by keeping this switch turned on, VR / IS will look for camera vibration and when it doesn’t find it, it keeps looking. Hence in itself causing camera shake. So I went out the next night with IS turned off and captured the image seen below.

The basic pattern of this electrical activity was first discovered over a hundred years ago. It comprises three waves, which have been named P, QRS (a wave complex), and T (see Figure 4).

However you do need to make sure your shutter speed is longer than the focal length of the lens. For example, when you zoom your lens out to 200mm, make sure the shutter speed is at minimum 1/200th of a second or faster. If you zoom it to 300mm focal length, then the shutter speed needs to be at least 1/300th of a second and so forth. This will give you the best chance of getting a sharp image while hand holding your camera.

Another six electrodes, placed in standard positions on the chest wall, give rise to a further six unipolar leads – the chest leads (also known as precordial leads), V1–V6. The potential difference of a chest lead is recorded between the relevant chest electrode and an estimate of zero potential – derived from the average potential recorded from the three limb leads.

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Left ventricular hypertrophy (LVH) is one of the easiest and most useful diagnoses to make (see Figure 12). The Sokolow–Lyon index is the most commonly calculated index of estimation. Does the sum of the S wave in lead V1 (SV1) and the R wave in V6 (RV6) add up to more than 3.5 mV, ie, 35 small or seven big squares? If so, the patient has LVH by voltage criterion. Right ventricular hypertrophy is indicated by a dominant R wave in V1 (ie, R wave bigger than following S wave; Sokolow–Lyon index: R in V1 + S in V5 or V6 ≥ 1.05 mV) and right axis deviation.

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Look on the side of your lens and check if it has a focus limit switch. You will recognize it because it will have a distance metering associated with it. For example my Canon lens has a switch on the side that says 1.8m -∞, as well as 6.5m-∞. If your lens doesn’t have this switch then ignore this section.

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This is the hallmark of atrial fibrillation (see Figure 7). Sometimes the baseline appears "noisy" and sometimes it appears entirely flat. However, if there are no P waves and the QRS complexes appear at randomly irregular intervals, the diagnosis is atrial fibrillation.

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For example, I live in a coastal town where I photograph boats anchored out at sea with islands in the background. If I use a wide angle landscape lens, the islands in the background seem much smaller and insignificant than when I use my telephoto zoom lens. For these types of shots I prefer to see layers. Hence, I’ll use my telephoto zoom lens.

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(a) A horizontal section through the chest showing the orientation of the chest leads with respect to the chambers of the heart. (b) In lead V1, depolarization of the interventricular septum occurs towards the lead, thus creating an upward deflection (more...)

Besides the stethoscope, the electrocardiogram (ECG) is the oldest and most enduring tool of the cardiologist. A basic knowledge of the ECG will enhance the understanding of cardiology (not to mention this book).

A wide QRS complex despite sinus rhythm is the hallmark of bundle branch block. Left bundle branch block (LBBB) can cause the ECG to look extremely abnormal (see Figure 13). When faced with such an ECG – after calculating rate, rhythm, and axis – check the width of the QRS complex. If it is more than three small squares wide, it is abnormal. Bundle branch block can then be diagnosed by pattern recognition of the QRS complexes in the V1 and V6 leads (see Figure 14). New LBBB can be diagnostic of myocardial infarction (MI).

Since the direction of a deflection, upward or downward, is dependent on whether the electrical activity is going towards or away from a lead, it differs according to the orientation of the lead with respect to the heart (see Figure 5).

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The first electrical resuscitation of a human took place (almost certainly) in 1872. The resuscitation of a drowned girl with electricity is described by Guillaume Benjamin Amand Duchenne de Boulogne, a pioneering neurophysiologist, in the third edition of his textbook on the medical uses of electricity. Although it is sometimes described as the first artificial pacing, the stimulation was of the phrenic nerve and not the myocardium.

A sawtooth waveform signifies atrial flutter (see Figure 8). The number of atrial contractions to one ventricular contraction should be specified.

The QT interval should be less than half of the R–R interval. Calculation of the corrected QT (QTc) is generally not necessary and usually will have been done by the ECG machine (but beware of blindly believing any automated diagnostic system). Conditions associated with a long QT interval are outlined in Table 3 (see Figure 18).

ECG demonstrating left ventricular hypertrophy. Note also the T-wave inversion in leads V4–V6. This is often labeled "strain".

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When photographers hear the term telephoto they usually imagine a long lens between 70 and 500mm focal length or longer. Personally I’ve used 3 different brands and the technique for using them is basically the same.

The ECG trace reflects the net electrical activity at a given moment. Consequently, activity in one direction is masked if there is more activity, eg, by a larger mass, in the other direction. For example, the left ventricle muscle mass is much greater than the right, and therefore its depolarization accounts for the direction of the biggest wave.

Blurring backgrounds is easier with a telephoto lens than it is with a wide angle lens. Set your camera aperture on f/8 or lower, zoom the lens out to its longest focal length, and get as close to the subject as possible while still being able to focus. You also need to ensure as much distance as possible between the subject and any background elements. You won’t see any blur if the subject is against a brick wall.

The absolute potassium level is less important than its rate of rise. ECG changes reflecting a rapid rise demand immediate action (see Figures 19–21). The level of danger increases as the ECG changes progress. The sequence generally follows the order:

A normal ECG tracing is provided in Figure 6. The only way to become confident at reading ECGs is to practice. It is important to be methodical – every ECG reading should start with an assessment of the rate, rhythm, and axis. This approach always reveals something about an ECG, regardless of how unusual it is.

A normal ECG has only very small Q waves. A downward deflection immediately following a P wave that is wider than two small squares or greater in height than a third of the subsequent R wave is significant: such Q waves can represent previous infarction (see Figure 11, previous page).

If you are photographing long exposures or landscapes with a telephoto lens then it is best to use a tripod. If using a tripod, look on the side of your lens for letters VR (vibration reduction for Nikon) or IS (image stabilization for Canon) and turn them off.

At every beat, the heart is depolarized to trigger its contraction. This electrical activity is transmitted throughout the body and can be picked up on the skin. This is the principle behind the ECG. An ECG machine records this activity via electrodes on the skin and displays it graphically. An ECG involves attaching 10 electrical cables to the body: one to each limb and six across the chest.