Sudden cardiac death
One of the most serious complications that high blood pressure can promote is undoubtedly sudden cardiac death (SCD). In the vast majority of cases this is fatal. Only about 2 to 5 percent of affected people reach the hospital alive. Even then, about half of these patients still die.
Sudden cardiac death describes a natural death with a cardiac, i.e. heart-related, cause. An existing heart disease may be known, but the timing and circumstances of the death are unexpected. Sudden cardiac death is initiated by a sudden loss of consciousness and occurs within one hour after the onset of acute symptoms.
In about half of cases, symptoms can be noticed a few hours, or sometimes even days or weeks, beforehand. These include chest pain, shortness of breath, altered consciousness up to fainting, or palpitations. Many cases (the other 50 percent), however, give no prior warning.
In about half of cases, symptoms can be noticed a few hours, or sometimes even days or weeks, beforehand. These include chest pain, shortness of breath, altered consciousness up to fainting, or palpitations. Many cases (the other 50 percent), however, give no prior warning.
What happens?
In all cases of sudden cardiac death there is a change in the electrical properties of the heart muscle cells, which leads via arrhythmias, electromechanical dissociation, or immediate asystole (cardiac arrest) to sudden cardiac death.
Usually three factors are needed for this:
- structural heart disease,
- a temporary trigger, and
- an arrhythmia mechanism.
In 10 to 15 percent of cases there is a heart muscle disease (cardiomyopathy) that is not caused by CAD.
The remaining cases are due to other, rare causes.
Temporary triggers can include, for example, electrolyte disturbances (changes in blood salts), lack of oxygen (hypoxia), drugs, an electrical shock, but also stress or a strong vagal reaction (vagus nerve stimulation), and similar factors.
Arrhythmia mechanisms refer to faults or problems in the heart's electrical conduction system that disturb the heart's regular action.
The cardiac event often begins with ventricular tachycardia. That means one or both ventricles beat too fast, which then progresses to ventricular fibrillation. The heart is then no longer able to pump blood into the circulation. As a result, no oxygen is delivered to the cells. This is followed by asystole: the heart stops. In rarer cases, asystole develops from bradycardia-a heart rate that is too slow.
What to do?
Calling the emergency number 112 immediately-ideally, if you can already recognize this, indicating that the patient needs to be resuscitated-is the first step. To give the person a chance of survival, cardiopulmonary resuscitation (CPR) must be started right away. If available, using an AED (automated external defibrillator, sometimes called a public-use defibrillator) can drastically increase the chance of survival. However, it does not replace CPR; it is a tool that can restore a normal heart rhythm. The emergency dispatch center can give you telephone guidance on these measures until the emergency services arrive.
Sources:
This article is from Tensana – the leading app since 2011, helping hundreds of thousands of people monitor their blood pressure every day.
Our content is based on carefully researched, evidence-based data and is continuously updated (as of 11/2025).
Author Sabine Croci is a qualified medical assistant with many years of experience in internal medicine and cardiology practices as well as outpatient care, and has headed the specialist editorial team at Tensana since 2015. Thanks to her extensive additional qualifications as an emergency medical technician, first responder, and in various areas of therapy and emergency care, she provides well-founded, practical, and reliably verified information.
Author Sabine Croci is a qualified medical assistant with many years of experience in internal medicine and cardiology practices as well as outpatient care, and has headed the specialist editorial team at Tensana since 2015. Thanks to her extensive additional qualifications as an emergency medical technician, first responder, and in various areas of therapy and emergency care, she provides well-founded, practical, and reliably verified information.
