Like HowStuffWorks on Facebook!

Congestive Heart Failure 101

        Health | Heart

Heart failure, or congestive heart failure (CHF), is a very common disease, afflicting approximately 4.8 million Americans. While many other forms of heart disease have become less common in recent years, CHF has been increasing steadily. This may be because more people with other forms of heart disease survive longer but are left with damaged hearts, which leads to CHF. Also, as the elderly population increases, there are more people at high risk of developing CHF. Approximately 400,000 new CHF cases occur each year, and it is the most common diagnosis in hospital patients over 65.

In this article, we will discuss congestive heart failure -- its causes, its warning signs and how it can be treated.

The purpose of the heart is to pump blood, which contains oxygen and nutrients, to the rest of the body. CHF is simply the failure of the heart to perform this main function adequately. Of course, a lack of blood pumped to the body is only considered CHF if the heart actually receives a sufficient volume of blood from the incoming vessels in the first place (i.e., normal filling pressures). When there is not enough blood for the heart to pump out, the problem is not CHF.

CHF occurs when the flow of blood from the heart (cardiac output) decreases, or fluid backs-up behind the failing ventricle, or both. Physicians have several different ways of describing heart failure:

  • Unilateral heart failure: Because the heart is basically two pumps (right side, left side) in one, either side can fail independently of the other.
    • Left-sided heart failure: When the left ventricle can't pump out enough blood, it gets backed-up in the lungs (behind the left ventricle), causing pulmonary edema, a build-up of fluid in the lungs. Among other things, this brings about shortness of breath. Left-sided heart failure often leads to right-sided heart failure.
    • Right-sided heart failure: The right ventricle cannot pump out enough blood, causing fluid to back up in the veins and then in capillaries of the body (behind the right ventricle). Because of the back-up, fluid leaks out of the capillaries and builds up in the tissues, a condition called systemic edema. Edema is especially noticeable in the legs because the lower half of the body drains into the right side of the heart .

  • Directional heart failure:
    • Backwards heart failure: The ventricle is not pumping out all the blood that comes into it. This increases the ventricular filling pressure and systemic or pulmonary edema. In fact, the heart can only meet the needs of the body if the ventricular filling pressure is high.
    • Forward heart failure: The heart is not pumping out enough blood to meet the needs of the body. Because less blood reaches the kidneys, they conserve salt and water, which contributes to excess fluid retention and edema. Forward failure also decreases the blood flow to various organs, causing weakness and fatigue.

    Time-dependent heart failure:

    • Acute heart failure: This describes heart failure that occurs suddenly. A heart attack can cause acute heart failure if a large enough part of the heart muscle dies. When this happens, the heart cannot pump out enough blood, causing heart failure and pulmonary edema. This makes breathing very difficult and can lead to death. Acute heart failure can also occur when a heart valve suddenly stops functioning or the chordae tendineae, the muscle and cord that helps the mitral valve function properly, suddenly ruptures.
    • Chronic heart failure: This describes heart failure that develops gradually. The symptoms are subtle at first but become more acute over time.

  • Phasic heart failure: The heart can fail in either of the two phases of the cardiac cycle -- contraction (systole) and rest (diastole).
    • Systolic heart failure: The heart has difficulty contracting and pumping out enough blood. This causes weakness, fatigue and decreased ability to exercise.
    • Diastolic heart failure: The heart is unable to fill properly during diastole, usually due to increased filling pressure. This causes systemic or pulmonary edema or both.

  • Output vs. demand heart failure:
    • High-output heart failure Cardiac output is normal or a little bit high, but demand for blood flow is abnormally high (hyperthyroidism, anemia, severe infections). The heart is unable to deliver the increased amount of blood and fails.
    • Low-output failure Cardiac output is low, but demand for blood flow is normal. The heart is unable to meet this demand and fails. Low-output failure is more common than high-output failure.

/* Discovernator - full and tiny */ .discovernator #factContainer { margin: 0 70px; -moz-box-shadow: 0 0 5px #a3ccea; -webkit-box-shadow: 0 0 5px #a3ccea; box-shadow: 0 0 5px #a3ccea; } .discovernator .tri { position: relative; z-index: 3; } /* full*/ .mainDiscovernator .RandomFact.module { margin-bottom: 0; } .discovernator.full { width: 825px; height: 570px; padding: 0 0 38px 0; background: url('') no-repeat 0 0; } .discovernator.full h1 { width:515px; height:122px; background: url('') no-repeat 130px 15px; } .discovernator.full h2 { width:498px; height:23px; background:url('') no-repeat 50px 0px; } .discovernator.full .button { width:233px; height:51px; background: url('') no-repeat 0 0; } .discovernator.full .tri { background-image: url (data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAEYAAAAlCAMAAADIkG9CAAAAulBMVEX////8/f72+v37/f7P5vP0+f2x1+zO5fOy2O3w9/u12e7y +Py83e/g7/j9/f74/P3l8Pi/3u/m8vjb7Pbe7ffF4PHE4PDL4/Pa7Pay1+3T5/Tt9fv9/v7W6vXM5fO02O293e/u9vuz2O3F4fHr9fr4+/3n8vnq9Pr +/v/Y6/X0+fz6/P3d7ffG4vG+3e/V6fXj8Pi52u7X6vXK4/K42u7B3/Dz +fzl8fjv9vvJ4/Lo8/nA3vC72+6w1uxDqvEIAAAAPnRSTlP//////////////////////////////////////////////////////////////////////////// /////ALr7cTYAAAEjSURBVEjHrdRndoJAFIbhQZEWiIDdaDSa3nt/97+t/OEkEgemyLeA58wtcwW/aQvr7IkmmHa8wbSsmRFNMD2aYFJKTNdOOZ6UGbsWHy0oM4 6NcrCizARWFQX8Yx4slLxQNpjMatJbzNoU2XeRMK6hcpkhY8Zmyv0KKfNmgjguyJl3k8MQU8F4+ts36wVUMUv9xV1CJaM7qK4PNUxfT0kW1DKh1nf +glomOlcj4Q0omEP1kEegZFIF0vFBzXhX9eX4HjrMRx3yOUCVgjmtPgdJDJpMNKtqyTwCbWYqf0g6QDMCwOvIBjyNwIjZXprWOMMkAuC1bJz0hxhGAE +ld1yvMY+AyV9nwotbrCJgXhyS3H/GNoJvRwjn7PGFXSJI8rshu+YHsJQatMLGNKcAAAAASUVORK5CYII=); } /* tiny*/ .discovernator.tiny { height: 304px !important; background: url('') no-repeat 0 0; } .discovernator.tiny h1 { margin: -8px -13px 0; width:300px; height: 82px; background: url('') no-repeat 0 0; } .discovernator.tiny h2 { margin: 6px auto 0; width:192px; height:30px; background: url('') no-repeat 0 0; } .discovernator.tiny #factContainer{ margin: -14px auto 0; height: 105px; } .discovernator.tiny #justthefacts li { padding: 16px 12px; height: 85px; } .discovernator.tiny #gimme { margin: 20px auto; } .discovernator.tiny .button { width:144px; height:31px; background: url('') no-repeat 0 0; } .discovernator.tiny .tri { background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACcAAAAVCAMAAADyzwehAAAAw1BMVEX/// +12O39/f7U6PT9/v7k8fiy1+zE4fH8/f7f7vjv9vvH4vLW6fX4/P34+/3E4PG52+6x1+zO5fO93O7L4/Oy2O3R5/P+/v/f7vf9/v/x +Pzh8Pjv9vv3+/3F4fG32u6z2O2x1uy42u7A3u/Y6/XY6vX1+v3b7Pbo8/nm8vjc7PfM5PP6/f79/v7T6PTt9frg7/jW6vW72+7n8/m62+70+f283e/j8Pjv9/v a7Pbm8vnu9fvE4PDQ5/PG4vHA3vCw1uzLlOswAAAAQXRSTlP/////////////////////////////////////////////////////////////////////////// //////////ADBV7McAAAC2SURBVCjPhc/XDoJAFEXRQUMLKMWu2HvB3uv5/68yCEHKDLOfV27OJYLXlHA6EXjpHJYzfLfjOBu +G2WzPAJ347HAqVnbqgidyGZtDaGTNkw2M/F3woSh3LGFiCs16MzpAFG3pKpCvoK4W9DebO2BuJMe6WHiB0i6kpJUcwNIu3VilzoEKK7vRFVTNwGqk2shKl7eEs BwhwCt7vYArAie7u+S+DoiI9K7EsWpa11kR+Rt+WyB2xegSVyWUNqfMQAAAABJRU5ErkJggg==); } /* twitter button*/ #twitternator i { background: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAC0AAAAoCAYAAABq13MpAAAGH0lEQVRYw +2Y30+TVxjHOTHOkUFCll0sXnFBNFmyhERvZrzo5S7J/APozW6WKU5BJz8LFkqopSDQX5ZSoFSkQPnpmNOBFGEotLQVms4RKlWrMClNxSb24ux53vZl/fECrh0/ sknyzVva857zeb/neZ7znpNCKU3ZSeScjEfy5Pz3aZusSJ4ih1xQGxnlKXhcbf5ufLYxO74DeQYpaLGQQj39pm1UkjTQ2SYeKHvL3y/c4JHiLkqEQ/TTmtveE9e HxdtCp15pW2AAzys3HU0r0VeRqp8ouTZKPxIOviEXm3OSgT5RNygmVzooKdBGjcPq4/Lu50Ryn5KmR5TUPWDgoW3LltBnuqbtRDRCSVkvNhwl +ZrMI5VDG6RhmhK5mRLpOD0s6PHDYBmJQj9+tZ57XGXyk+o7lAiMlPzY7iU/qASMy5da+aTmbmgspZUShYWS65MsuIATWmd/JmIaoQD +UOWwj9SOw81zlKhsoc6u/UpTyww6mEZjguBpjJOyGUoafmP6IxX9lBTdtHwiGn5Jrk +FgHE8lHKO4TkiHNhgHuz7hgwI48zIDrNO6ue8TEOm07DDbAconDYcSIDMibktefTUka6eC4bcnAvBozn1kyF3I8dDYRt80FIDPXRJa200PT4W1aHW/txAZLPhp 7RydGChuXeeuBdW/VOJQps962fSFA/fbfaPVzSKEceY7CxLTfQrzYTrS0nfKcbyiE6zc0ecbqYDjpvTVbPBP7wb +dDu8yQSMu27X5zOo632wJaQHGb1Lb62LPveYjXJSkktaNaR81Ab8+SZ5HIb7wv1pHXT7Zgbb9hePMJB/4V6zP/27hM7ZzjECgzMGXB40FB27JSlNb/gs8peMyn qpKQcMloyFhfL6c3WoGT2mQNuOP3Pa3NjNiiu4vy8uJJ/VGPe0W2cXdPyWnVs9UB6qeShy3FcO +Nnki0cHukaWzDn9hPP4z/f3IM2XyfoatbhgpZxWOGkuMLBjPLIRTU/VTjwgKlU20Bjwo65vfdjwzGyc4S6ARqN0CDocpIxnPLM91Z2UnlvCisAIyxz4nuhasQF Dd8d1doCYeCsLReXXRbO5uW+319ZTnaYvUyZYxeRGNjj+nm/xPwCQ/EmF/BeQm9WJwzFlbfvTFgNzt13LZ0bf7qEV83Cin3h9cZUeLa3DcW9ho50Hh +AH6HT7xuG+wWdlD5Af4D+X0IXFxfzSkpK +AcOuqioKG7vBqAZQqHQUlNTQ7u7uyUHDrq6unoBAcvKyjYdFYvFVXK5nGo0GtrU1PSmoqIi50BBDw0N2RUKBa2rq6MAP3r16tVMmUy2odfrqcFgoK2trbS +vt4PD5VxYKCdTqdIp9NRlFKppADs02q1GBa0t7eXAUfHpVKpTiAQGA9KImYNDw97e3p66K1btyjrMAKz6uzsZMDBcbpbQKWlpTnl5eVGFHzm7Vg9wG1DV1cXA4 jwkcCs25OTk+61tbWE9ohYhUBbHtbADPIkEgnmD1WpVN6Wlhbuw5rCwsKoPeLExISbCxgFoRL0+XwJ7xHVarUYEp7GJjwryKfnGJI4o +3t7Qw8tI0/rIEvdTglUN4yq6qqeOCmlXU71mWYiaT2iKurq7kQen5wkQkxkUjkBXeZgxgYmw8PxYyDpuEV8ysMHn1Ys76+LmhsbDRDeWM6gimJi2Wj0Ricn59P aI8Y +0qKTrI5g/nR0NBAYWwLlNaXHR0dUWGJn8PgzGENRgWsJ5mbe0Sbzebo6+vzY4fsjf39/UGTyeTxer3J7BGjZLfbHWgCjoGVCeHxQRAu1qxwSDK/19bW0srKSuv 09PSxPdkjRmplZeUMhN871hi8Roorl/Bh2tra8OqCcnxqX3YtUIGcg4ODga0guaCXl5ctfr8/dFizTwsEH8DtXOEQK3ywsbGx6MOa3QbEFzFQ3NIPzuVDbO/oNv we9Hg81Xv9Pp0FJWscVjgprnBQWnnw4sWHivUAk287aExYAN72sGbXBLEog3I2hRUAhWWuubmZRlaq2JAYGBgIhIH397DG5XJZIAG97HtNLDD +PzIy4nfA34E7rAkEAia3222ZmZlZmp2dXcLr4uKiHRa6/+5hzV9kwTJynia+aQAAAABJRU5ErkJggg==") no-repeat -24px 0; height: 18px; width: 20px; margin-left: 8px; }