The apex of the heart is lowest tip of the organ that points downward at the base, forming what almost looks like a rounded point. “Apex” is a Latin word meaning “summit” or “peak,” and this part of the heart can be thought of in those terms, too. It’s formed mostly by the left ventricle and extends pretty far out to the left in most people. The muscle fibers in this part of the heart are primarily responsible for regulating ventricle contraction, and also play an important role when it comes to relaying and transmitting signals from atrial nodes. Medical professionals often pay particular attention to this peak during physical exams, too. It can be a good place to listen to the beating of the heart since its location often offers clarity without a lot of competing noise, for instance, and it’s one of the four most common heart listening areas. Signals that aren’t coming through the apex as strongly or as frequently as they once did may also be an early sign of heart enlargement or failure.
The main job of the apex from a physiological standpoint is to cause the heart’s ventricles to contract from the bottom up. This provides the driving force that sends the blood up and out of the heart. In most cases this efficiency is the result of the combined efforts of a range of atrial nodes and signal fibers, and the shape of the heart, particularly the way the apex is formed in the left ventricle, is also useful when it comes to acting as a conductor. Signals can quickly go down and around at the peak, and can exit as quickly as they entered.
Regulating the contractions of the ventricles so they are well-timed to the contractions of the atrium is really important to heart health and overall health, too — but the process isn’t always as easy as it might seem. The timing is the result of a system of fibers that runs from the top of the atrium to the apex, where the fibers break into two pathways leading to the left and right ventricles. These fibers found within the walls of the heart are known as Purkinje fibers.
The function of Purkinje fibers is to conduct impulses rapidly. They are arranged within the heart and contract to make the heart’s rhythm most efficient. The fibers work together with a few nodes to stimulate and regulate the impulses.
The sinoatrial (SA) nodes are areas of the heart's atrium that act as the heart's pacemaker. Impulses from the SA node cause the heart’s chambers to contract. Purkinje fibers receive their impulses from the SA node and move the impulse through the heart’s muscles.
Just below the atrium is another node, the atrioventricular (AV) node, which slows the impulses from the SA node. This slower signal proceeds to the apex of the heart and then around to the left and right ventricles. The timing of the impulses from the SA node to the AV node and on to the ventricles is ideally perfect for the flow of blood. Once the blood has reached the ventricles, the Purkinje fibers signal for these spaces to contract.
Location and Listening
The heart sits more on the left side of the body than on the right side in most people, and locating the apex usually starts by identifying just where the heart begins and ends. In most people the peak point is somewhere in the vicinity of the fifth intercostal space. The numbering of intercostal spaces — basically the space between two ribs — is done according to the upper rib, so the fifth intercostal space is between the fourth and fifth ribs. The apex is found at this level and typically around 3 to 3.5 inches (8 to 9 cm) from the sternum.
The apex is one of four primary “listening places” for physicians and other caregivers, alongside the second right and left intercostal spaces and the fourth left intercostal space. It’s often believed that the heart’s beating can be best heard here, and there’s also a clarity in these spaces that can help care providers identify problems like murmurs and irregular beats more quickly.
Detecting Heart Problems
Irregularities in the way the apex directs signals can also be an early warning sign for heart disease. Heart impulses can’t usually be detected simply by listening with a stethoscope, but a heart scan or electrocardiograph (ECG) scan will usually pick them up. When the apex isn’t emitting the same signals as it used to, it can indicate heart enlargement or early failure. Both of these are usually treatable, but the sooner they’re identified the better.
Where Is the Apex of the Heart?
The heart is a muscular organ that weighs roughly 1/2-3/4 of a pound and is about the size of a person's fist. The heart is generally in proportion to overall body size, so a person with a smaller body has a smaller heart and a larger person has a larger one. Much of the heart is simply muscle tissue around enclosed spaces. These spaces are known as the chambers of the heart. Their arrangement is important for allowing the heart to pump blood to all points of the body.
The apex of the heart is the sharpest point of it, which is located at the bottom and angles down and forward. There is a longitudinal line from the center of the heart's base to the apex, which is known as its anatomical axis. Since the 1940s, most anatomical studies show that a normal heart lies at an angle of 20-40 degrees. However, there are different types of physiological phenomena that can cause the heart to move on its anatomical axis. This will also usually affect cardiac function.
The Left vs. Right Ventricular Apex
The apex of the heart is the most anterior, inferior, and lateral part of the heart and is located along the midclavicular line. Situated along the fifth intercostal space, it is formed by the left and right ventricles.
The left ventricle is the heart's main powerhouse that pumps blood through the entire circulatory system. Since it has such a big job, it also has the strongest and most muscular walls compared to the other chambers of the heart. It's three times as muscular as the right ventricle, in fact. The cone-shaped cavity features two papillary muscles as well as a strong trabeculae carneae and does not have a moderator band. The cross-section of the left ventricle is circular to accommodate the bulging of the interventricular septum as it spans into the right ventricle. This happens because blood pressure is six times higher in the left ventricle as compared to the right. The apex portion of the left ventricle has thinner walls.
The apex portion of the right ventricle sits at the bottom of the right ventricle, close to but separated from the left ventricle's apex by the interventricular septal wall. The right ventricle contains deoxygenated blood and connects to the right atrium with the help of the tricuspid valve, the pulmonary trunk, and the pulmonary semi-lunar valve. Although not as muscular as the left ventricle, the right ventricle is still quite muscular in its own right. It features a series of trabeculae carneae, which are muscular ridge-like structures. One of these ridges is able to disconnect partially and forms the moderator band that runs between the anterior papillary muscle and the interventricular septum. It works as part of the conducting system of the heart. When the right ventricle contracts, the blood forces itself through the pulmonary circulation and into the left atrium.
What Is the Function of the Heart Apex?
The apex of the heart is known for creating the apex beat, which is the beating of the heart that a person feels when touching his or her chest. This occurs because the area of the muscle touches the walls of the chest as it beats. Beating occurs when the left ventricle pumps blood into the right ventricle, moving it through the aortic valve and arch in a continuous cycle.
The apex beat, which is also called the apical impulse, is felt at the point of maximum impulse (also known as the PMI), which is quite near the apex of the heart. A medical professional can find an adult person's apex beat in the left fifth intercostal space, which is about 3-4 inches left of the sternum's left border and a half-inch to the left of the midclavicular line. In children, the beat is in the fourth rib interspace. Some people have their apex beats in abnormal locations. For example, dextrocardia patients may have their apex beats on their right sides.
The Importance of the Apex Beat
The apex beat is important for various medical interpretations. If the beat is displaced laterally or has an inferior displacement, it may indicate an enlarged heart. Other conditions, such as pulmonary diseases or deformities of the thoracic vertebrae are also indicated by this type of displacement. There are several other ways medical professionals can use the apex beat to determine health situations as well. A pulse deficit may indicate arrhythmias, while hypertension or aortic stenosis may be indicated by a sustained apex beat, most specifically a prolonged upward cardiac force.