The ECG in Patients with Palpitations and Syncope: Between Attacks

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The ECG in Patients with Palpitations and Syncope


Between Attacks



The ECG is of paramount importance for the diagnosis of arrhythmias. Many arrhythmias are not noticed by the patient, but often they cause symptoms. These symptoms are often transient, and the patient may be completely well at the time he or she consults a doctor. Obtaining an ECG during a symptomatic episode is then the only certain way of making a diagnosis, but as always the history and physical examination are also extremely important. The main purpose of the history and examination is to help decide whether a patient’s symptoms could be the result of an arrhythmia, and whether the patient has a cardiac or other disease that may cause an arrhythmia.



THE CLINICAL HISTORY AND PHYSICAL EXAMINATION



PALPITATIONS


‘Palpitations’ mean different things to different patients, but a general definition would be ‘an awareness of the heartbeat’. Arrhythmias, fast or slow, can cause poor organ perfusion and so lead to syncope (a word used to describe all sorts of collapse), breathlessness and angina. Some rhythms can be identified from a patient’s description, such as:



Table 2.1 compares the symptoms associated with sinus tachycardia and a paroxysmal tachycardia, and shows how a diagnosis can be made from the history. Note that a heart rate between 140/min and 160/min may be associated with either sinus or paroxysmal tachycardia.




DIZZINESS AND SYNCOPE


These symptoms may have a cardiovascular or a neurological cause. Remember that cerebral hypoxia, however caused, may lead to a seizure, and that can make the differentiation between cardiac and neurological syncope very difficult. Syncope is defined as ‘a transient loss of consciousness characterized by unresponsiveness and loss of postural tone, with spontaneous recovery and not requiring specific resuscitative intervention’.


Figure 2.1 shows an EEG that was being recorded in a 46-year-old woman with episodes of limb shaking, suspected of being generalized tonic-clonic seizures. She lost awareness during events, and had violent limb shaking for several seconds as she came round. She felt nauseated, but was rapidly reorientated. By chance, she had one of her ‘attacks’ while her EEG was being recorded, and from the ECG being routinely recorded in parallel, it became clear that the problem was not seizures, but periods of asystole – in this case lasting about 15 s. The numbered arrows in Figure 2.1 mark significant features. The recording begins with a routine period of hyperventilation, with the EEG showing an eye blink in the anterior leads and the ECG showing sinus rhythm. There are then (at arrow 1 on the record) one (or possibly two) ventricular extrasystoles, followed by a narrow complex beat (probably sinus) and another ventricular extrasystole, with a different configuration from the previous ones. Asystole follows, and after 7–8 s (at arrow 2) there is global EEG slowing, and the patient became unresponsive. After 4 s (at arrow 3), there is global attenuation (reduction in signals) in the EEG and after another 3 s, there is an escape beat whose morphology suggests a ventricular origin. This is followed by a beat with a narrow QRS complex and possibly an inverted T wave, and then there is gross artefact due to the ECG lead being checked. During that period, sinus rhythm was restored. There was then (at arrow 4) global EEG slowing for 5 s, followed by (at arrow 5) violent limb thrashing for about 12 s as the patient regained consciousness – these movements were not clonic, and were thought to represent anxiety or fear. Normal EEG and ECG activity were then resumed (at arrow 6).



Some causes of syncope are summarized in Box 2.1.


Table 2.2 shows some clinical features of syncope, and possible causes.





PHYSICAL EXAMINATION


If the patient has no symptoms at the time of the examination, look for:



It is only possible to make a confident diagnosis that an arrhythmia is the cause of palpitations or syncope if an ECG recording of the arrhythmia can be obtained at the time of the patient’s symptoms. If the patient is asymptomatic at the time of examination, it may be worth arranging for an ECG to be recorded during an attack of palpitations, or to be recorded continuously, in the hope that an episode of the arrhythmia will be detected.



THE ECG


Even when the patient is asymptomatic, the resting ECG can be very helpful, as summarized in Table 2.3.




SYNCOPE DUE TO CARDIAC DISEASE OTHER THAN ARRHYTHMIAS


The ECG may indicate that syncopal attacks have a cardiovascular cause other than an arrhythmia.


ECG evidence of left ventricular hypertrophy or of left bundle branch block may suggest that syncope is due to aortic stenosis. The ECGs in Figures 2.2 and 2.3 were recorded from patients who had syncopal attacks on exercise due to severe aortic stenosis.




ECG evidence of right ventricular hypertrophy suggests thromboembolic pulmonary hypertension. The ECG in Figure 2.4 is that of a middle-aged woman with dizziness on exertion, due to multiple pulmonary emboli.



Syncope due to hypertrophic cardiomyopathy ( Fig. 2.5) may be associated with a characteristic ECG ( Fig. 2.6) that resembles that of patients with an anterior non-ST segment elevation myocardial infarction (NSTEMI) (compare with Fig. 5.23, p. 240). With hypertrophic cardiomyopathy, the T wave inversion is usually more pronounced than with an NSTEMI, but differentiation really depends on the clinical picture, not on the ECG appearance. Hypertrophic cardiomyopathy can cause syncope due to obstruction to outflow from the left ventricle, or can cause symptomatic arrhythmias.





PATIENTS WITH POSSIBLE TACHYCARDIAS



MITRAL STENOSIS


Mitral stenosis leads to atrial fibrillation, but when the heart is still in sinus rhythm the presence of the characteristics of left atrial hypertrophy on the ECG may give a clue that paroxysmal atrial fibrillation is occurring ( Fig. 2.7).


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Jul 26, 2016 | Posted by in CARDIOLOGY | Comments Off on The ECG in Patients with Palpitations and Syncope: Between Attacks

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