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Posted on Thursday May 9, 2024 in Naked Heart
The Naked Heart is an educational project owned and operated by Dr Edward Leatham. It comprises a series of blog articles, videos and reels distributed on Tiktok, Youtube and Instagram aimed to help educate both patients and healthcare professionals about cardiology related issues.
Blood pressure management is a crucial aspect of maintaining cardiovascular health. My belief is that the best blood pressure to have in mid life for the best longevity and freedom from heart failure in later life is for it to be as low as possible without having side effects. However, the pursuit of optimal blood pressure can sometimes be a challenging journey for many patients, who frequently ask why their blood pressure has risen over time. Many recall having lower readings in their youth and are baffled by its current elevation, despite careful attention to their diet and salt intake.
The story begins over 2 million years ago when most mammals (including humans) died of sepsis, injury and accidents. Species survival created evolutionary pressure for protective systems that counter low blood pressure or ‘shock’, where organ failure occurs as a result of low blood pressure. These ‘flight, fight or fright’ pathways act to increase blood pressure in crisis and include adrenaline release, neural and blood borne pathways that cause peripheral constriction, and salt (Sodium Chloride) and water retention. In regions of sub-Saharan Africa that are naturally devoid of salt, mutations occurred that helped our ancestors living in these regions to survive and propagate despite minimal dietary intake of salt. Following migration out of Africa 50-70 thousand years ago and with the arrival of salt (Sodium Chloride) as a preservative from the middle ages, the genetic and environmental triggers for modern day hypertension were set. In the Middle Ages, salt became a favored method of preserving food, and it remains prevalent in modern diets and food processing.
These genetic adaptations are now widespread in modern society. Those fortunate enough to inherit genes that code for blood pressure that is not sensitive to salt intake will generally tend to remain normotensive throughout life. However, for a significant proportion of the population, perhaps related to inheriting genes tracing back to prehistoric ancestors surviving in sub-Saharan Africa, their salt (Sodium Chloride) intake may be sufficient to trigger physiological changes that lead to hypertension developing, especially after their second decade of life.
The interaction between genetics and dietary salt intake explains the broad range of blood pressure values we see today, heavily influenced by inherited traits. This phenomenon explains why patients with hypertension often appear to have a genetic predisposition, with one or both parents suffering from hypertension or related conditions like atrial fibrillation, stroke, or heart failure.
Animal models of hypertension (such as knockout rat models), show a clear link between salt intake in mammalian early life and blood pressure later. In essence, dietary salt consumption during the first two decades of life may well program future blood pressure, explaining why only a small proportion (10%) of adult patients with essential hypertension are ‘salt sensitive’ – meaning that their blood pressure can be lowered somewhat by adopting a salt-free diet. For the majority of adult hypertensive patients, despite the likely importance of salt as a contributory cause of their hypertension, adopting a low salt diet as part of treatment yields disappointing results- it literally is a case of ‘too little too late’. This concept highlights the importance of reducing salt intake in children and young adults, especially in families genetically prone to hypertension. Lobbying for healthier food production practices, particularly in schools, and encouraging low-salt diets at home is probably going to turn out to be the only way that reducing dietary salt intake can significantly reduce the risk of high blood pressure occurring later in adults life.
The human heart beats around a billion times in an average lifetime. This incredible workload can manage higher blood pressures without much difficulty when life expectancy was short. However, as people live longer, maintaining optimal blood pressure becomes increasingly important to reduce decades of strain on the heart and prolong its functionality. Aging stiffens all muscles, including the heart. Diastolic heart failure (often referred to as ‘Heart failure with preserved Ejection Fraction’ of ‘HFpEF’) is becoming one of the commonest conditions of the elderly and a major cause for hospitalisation. It arises from ventricular stiffening due to age, hypertension, and various other rarer heart conditions. The aging component of this process is unavoidable, but maintaining optimal blood pressure through midlife is achievable and, if successful, should prevent additional left ventricular stiffening attributed to hypertension. By regularly monitoring blood pressure and using effective medication, we can help patients live longer with healthier hearts.
Answering this is akin to asking, “How long is a piece of string?” Severe hypertension (above 150/90 mmHg) clearly increases short term health risks, requiring aggressive treatment. However, opinions vary on the ideal lower limit. The latest UK NICE guidelines recommends clinic recordings <140/90 mmHg [1], however blood pressure fluctuates throughout the day, so what appears suitable in the morning may lead to symptoms of low blood pressure in the afternoon.
Large studies have shown that targeting lower blood pressure in higher risk patients reduces the risk of heart failure and adverse outcomes. A reading of 120/70 mmHg is associated with a lower future risk than 130/80 mmHg, and certainly much lower than 140/80 mmHg. Clinical trials confirm that aggressively lowering blood pressure below current guideline values reduces heart failure and other complications, even though it can sometimes lead to low blood pressure symptoms [2] . It should be remembered however that the evidence is less strong for lowering diastolic blood pressure below 80 mmHg, indeed some trials showed higher coronary event rates when diastolic blood pressure is lowered below 70 mmHg [3], where, it is postulated , reduced coronary perfusion might occur. An individualised approach to target setting is therefore recommended.
When offered the choice, most patients prefer to run the risk of transient episodes of low blood pressure, which can be managed by drinking more fluids , care when rising or sometimes reclining for a short period, rather than accepting higher blood pressure with the considerable chance of recurrent hospital admissions for heart failure or suffering a stroke in later life. Thus, aggressive treatment of hypertension is advisable both in middle age and later life.
Hypertension is linked to increased risk of the dreaded stroke, though its impact on coronary disease is comparatively smaller. However the larger benefits of lower blood pressure lie in preventing arrhythmias and heart failure in later life. Many patients prone to atrial arrhythmias can have their condition managed by simply reducing blood pressure, rather than relying on antiarrhythmic drugs. Although not fully tested in clinical trials, reducing blood pressure also reduces the pressure and stretch of the left atrium which appear to lower the likelihood of atrial fibrillation, especially in those with borderline hypertension.
When asked what constitutes the best blood pressure, my advice is that the lower the value, the better, as long as significant side effects are avoided. Personally, my blood pressure averages 100/60 mmHg, without medication. While this sometimes makes me feel lightheaded when standing up on hot days or after a hot bath, I recognize these symptoms as a minor inconvenience in exchange for the long-term benefits of a healthy heart.
In summary, the goal is to find a balance that achieves the lowest possible blood pressure without debilitating side effects. By understanding the genetic, dietary, and lifestyle factors that affect blood pressure, and by using modern treatments like ACE inhibitors, calcium channel blockers, and spironolactone, we can support healthier hearts and improve longevity across the population.
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